Source/WebCore/rendering/RenderLayerBacking.cpp

/*
 * Copyright (C) 2009, 2010, 2011 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */

#include "config.h"

#if USE(ACCELERATED_COMPOSITING)

#include "RenderLayerBacking.h"

#include "AnimationController.h"
#include "CanvasRenderingContext.h"
#include "CSSPropertyNames.h"
#include "CachedImage.h"
#include "Chrome.h"
#include "FontCache.h"
#include "FrameView.h"
#include "GraphicsContext.h"
#include "GraphicsLayer.h"
#include "HTMLCanvasElement.h"
#include "HTMLIFrameElement.h"
#include "HTMLMediaElement.h"
#include "HTMLNames.h"
#include "HTMLPlugInElement.h"
#include "InspectorInstrumentation.h"
#include "KeyframeList.h"
#include "MainFrame.h"
#include "PluginViewBase.h"
#include "ProgressTracker.h"
#include "RenderFlowThread.h"
#include "RenderIFrame.h"
#include "RenderImage.h"
#include "RenderLayerCompositor.h"
#include "RenderEmbeddedObject.h"
#include "RenderNamedFlowFragment.h"
#include "RenderRegion.h"
#include "RenderVideo.h"
#include "RenderView.h"
#include "ScrollingCoordinator.h"
#include "Settings.h"
#include "StyleResolver.h"
#include "TiledBacking.h"
#include <wtf/text/StringBuilder.h>

#if ENABLE(CSS_FILTERS)
#include "FilterEffectRenderer.h"
#if ENABLE(CSS_SHADERS)
#include "CustomFilterOperation.h"
#endif
#endif

#if ENABLE(WEBGL) || ENABLE(ACCELERATED_2D_CANVAS)
#include "GraphicsContext3D.h"
#endif

using namespace std;

namespace WebCore {

using namespace HTMLNames;

static bool hasBoxDecorationsOrBackgroundImage(const RenderStyle*);
static IntRect clipBox(RenderBox& renderer);

static inline bool isAcceleratedCanvas(RenderObject* renderer)
{
#if ENABLE(WEBGL) || ENABLE(ACCELERATED_2D_CANVAS)
    if (renderer->isCanvas()) {
        const HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer->node());
        if (CanvasRenderingContext* context = canvas->renderingContext())
            return context->isAccelerated();
    }
#else
    UNUSED_PARAM(renderer);
#endif
    return false;
}

// Get the scrolling coordinator in a way that works inside RenderLayerBacking's destructor.
static ScrollingCoordinator* scrollingCoordinatorFromLayer(RenderLayer& layer)
{
    Page* page = layer.renderer().frame().page();
    if (!page)
        return 0;

    return page->scrollingCoordinator();
}

bool RenderLayerBacking::m_creatingPrimaryGraphicsLayer = false;

RenderLayerBacking::RenderLayerBacking(RenderLayer& layer)
    : m_owningLayer(layer)
    , m_scrollLayerID(0)
    , m_artificiallyInflatedBounds(false)
    , m_isMainFrameRenderViewLayer(false)
    , m_usingTiledCacheLayer(false)
    , m_requiresOwnBackingStore(true)
#if ENABLE(CSS_FILTERS)
    , m_canCompositeFilters(false)
#endif
    , m_backgroundLayerPaintsFixedRootBackground(false)
    , m_didSwitchToFullTileCoverageDuringLoading(false)
{
    Page* page = renderer().frame().page();

    if (layer.isRootLayer() && page) {
        if (renderer().frame().isMainFrame())
            m_isMainFrameRenderViewLayer = true;

        m_usingTiledCacheLayer = page->chrome().client().shouldUseTiledBackingForFrameView(renderer().frame().view());
    }
    
    createPrimaryGraphicsLayer();

    if (m_usingTiledCacheLayer && page) {
        TiledBacking* tiledBacking = this->tiledBacking();

        tiledBacking->setIsInWindow(page->isInWindow());

        if (m_isMainFrameRenderViewLayer)
            tiledBacking->setUnparentsOffscreenTiles(true);

        tiledBacking->setScrollingPerformanceLoggingEnabled(page->settings().scrollingPerformanceLoggingEnabled());
        adjustTiledBackingCoverage();
    }
}

RenderLayerBacking::~RenderLayerBacking()
{
    updateAncestorClippingLayer(false);
    updateDescendantClippingLayer(false);
    updateOverflowControlsLayers(false, false, false);
    updateForegroundLayer(false);
    updateBackgroundLayer(false);
    updateMaskLayer(false);
    updateScrollingLayers(false);
    detachFromScrollingCoordinator();
    destroyGraphicsLayers();
}

void RenderLayerBacking::willDestroyLayer(const GraphicsLayer* layer)
{
    if (layer && layer->usingTiledBacking())
        compositor().layerTiledBackingUsageChanged(layer, false);
}

std::unique_ptr<GraphicsLayer> RenderLayerBacking::createGraphicsLayer(const String& name)
{
    GraphicsLayerFactory* graphicsLayerFactory = 0;
    if (Page* page = renderer().frame().page())
        graphicsLayerFactory = page->chrome().client().graphicsLayerFactory();

    std::unique_ptr<GraphicsLayer> graphicsLayer = GraphicsLayer::create(graphicsLayerFactory, this);

#ifndef NDEBUG
    graphicsLayer->setName(name);
#else
    UNUSED_PARAM(name);
#endif
    graphicsLayer->setMaintainsPixelAlignment(compositor().keepLayersPixelAligned());

#if PLATFORM(MAC) && USE(CA)
    graphicsLayer->setAcceleratesDrawing(compositor().acceleratedDrawingEnabled());
#endif    
    
    return graphicsLayer;
}

bool RenderLayerBacking::shouldUseTiledBacking(const GraphicsLayer*) const
{
    return m_usingTiledCacheLayer && m_creatingPrimaryGraphicsLayer;
}

void RenderLayerBacking::tiledBackingUsageChanged(const GraphicsLayer* layer, bool usingTiledBacking)
{
    compositor().layerTiledBackingUsageChanged(layer, usingTiledBacking);
}

TiledBacking* RenderLayerBacking::tiledBacking() const
{
    return m_graphicsLayer->tiledBacking();
}

static TiledBacking::TileCoverage computeTileCoverage(RenderLayerBacking* backing)
{
    // FIXME: When we use TiledBacking for overflow, this should look at RenderView scrollability.
    FrameView& frameView = backing->owningLayer().renderer().view().frameView();

    TiledBacking::TileCoverage tileCoverage = TiledBacking::CoverageForVisibleArea;
    bool useMinimalTilesDuringLiveResize = frameView.inLiveResize();
    bool useMinimalTilesDuringLoading = false;
    // Avoid churn.
    if (!backing->didSwitchToFullTileCoverageDuringLoading()) {
        useMinimalTilesDuringLoading = !frameView.isVisuallyNonEmpty() || (frameView.frame().page()->progress().isMainLoadProgressing() && !frameView.wasScrolledByUser());
        if (!useMinimalTilesDuringLoading)
            backing->setDidSwitchToFullTileCoverageDuringLoading();
    }
    if (!(useMinimalTilesDuringLoading || useMinimalTilesDuringLiveResize)) {
        bool clipsToExposedRect = backing->tiledBacking()->clipsToExposedRect();
        if (frameView.horizontalScrollbarMode() != ScrollbarAlwaysOff || clipsToExposedRect)
            tileCoverage |= TiledBacking::CoverageForHorizontalScrolling;

        if (frameView.verticalScrollbarMode() != ScrollbarAlwaysOff || clipsToExposedRect)
            tileCoverage |= TiledBacking::CoverageForVerticalScrolling;
    }
    if (ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(backing->owningLayer())) {
        // Ask our TiledBacking for large tiles unless the only reason we're main-thread-scrolling
        // is a page overlay (find-in-page, the Web Inspector highlight mechanism, etc.).
        if (scrollingCoordinator->mainThreadScrollingReasons() & ~ScrollingCoordinator::ForcedOnMainThread)
            tileCoverage |= TiledBacking::CoverageForSlowScrolling;
    }
    return tileCoverage;
}

void RenderLayerBacking::adjustTiledBackingCoverage()
{
    if (!m_usingTiledCacheLayer)
        return;

    TiledBacking::TileCoverage tileCoverage = computeTileCoverage(this);
    tiledBacking()->setTileCoverage(tileCoverage);
}

void RenderLayerBacking::updateDebugIndicators(bool showBorder, bool showRepaintCounter)
{
    m_graphicsLayer->setShowDebugBorder(showBorder);
    m_graphicsLayer->setShowRepaintCounter(showRepaintCounter);
    
    if (m_ancestorClippingLayer)
        m_ancestorClippingLayer->setShowDebugBorder(showBorder);

    if (m_foregroundLayer) {
        m_foregroundLayer->setShowDebugBorder(showBorder);
        m_foregroundLayer->setShowRepaintCounter(showRepaintCounter);
    }
    
    if (m_contentsContainmentLayer)
        m_contentsContainmentLayer->setShowDebugBorder(showBorder);
    
    if (m_backgroundLayer) {
        m_backgroundLayer->setShowDebugBorder(showBorder);
        m_backgroundLayer->setShowRepaintCounter(showRepaintCounter);
    }

    if (m_maskLayer) {
        m_maskLayer->setShowDebugBorder(showBorder);
        m_maskLayer->setShowRepaintCounter(showRepaintCounter);
    }

    if (m_layerForHorizontalScrollbar)
        m_layerForHorizontalScrollbar->setShowDebugBorder(showBorder);

    if (m_layerForVerticalScrollbar)
        m_layerForVerticalScrollbar->setShowDebugBorder(showBorder);

    if (m_layerForScrollCorner)
        m_layerForScrollCorner->setShowDebugBorder(showBorder);

    if (m_scrollingLayer)
        m_scrollingLayer->setShowDebugBorder(showBorder);

    if (m_scrollingContentsLayer) {
        m_scrollingContentsLayer->setShowDebugBorder(showBorder);
        m_scrollingContentsLayer->setShowRepaintCounter(showRepaintCounter);
    }
}

void RenderLayerBacking::createPrimaryGraphicsLayer()
{
    String layerName;
#ifndef NDEBUG
    layerName = m_owningLayer.name();
#endif
    
    // The call to createGraphicsLayer ends calling back into here as
    // a GraphicsLayerClient to ask if it shouldUseTiledBacking(). We only want
    // the tile cache on our main layer. This is pretty ugly, but saves us from
    // exposing the API to all clients.

    m_creatingPrimaryGraphicsLayer = true;
    m_graphicsLayer = createGraphicsLayer(layerName);
    m_creatingPrimaryGraphicsLayer = false;

    if (m_usingTiledCacheLayer)
        m_childContainmentLayer = createGraphicsLayer("TiledBacking Flattening Layer");

    if (m_isMainFrameRenderViewLayer) {
        m_graphicsLayer->setContentsOpaque(true);
        m_graphicsLayer->setAppliesPageScale();
    }

#if PLATFORM(MAC) && USE(CA)
    if (!compositor().acceleratedDrawingEnabled() && renderer().isCanvas()) {
        const HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer().element());
        if (canvas->shouldAccelerate(canvas->size()))
            m_graphicsLayer->setAcceleratesDrawing(true);
    }
#endif    
    
    updateOpacity(&renderer().style());
    updateTransform(&renderer().style());
#if ENABLE(CSS_FILTERS)
    updateFilters(&renderer().style());
#endif
#if ENABLE(CSS_COMPOSITING)
    updateLayerBlendMode(&renderer().style());
#endif
}

void RenderLayerBacking::destroyGraphicsLayers()
{
    if (m_graphicsLayer) {
        willDestroyLayer(m_graphicsLayer.get());
        m_graphicsLayer->removeFromParent();
    }

    m_ancestorClippingLayer = nullptr;
    m_contentsContainmentLayer = nullptr;
    m_graphicsLayer = nullptr;
    m_foregroundLayer = nullptr;
    m_backgroundLayer = nullptr;
    m_childContainmentLayer = nullptr;
    m_maskLayer = nullptr;

    m_scrollingLayer = nullptr;
    m_scrollingContentsLayer = nullptr;
}

void RenderLayerBacking::updateOpacity(const RenderStyle* style)
{
    m_graphicsLayer->setOpacity(compositingOpacity(style->opacity()));
}

void RenderLayerBacking::updateTransform(const RenderStyle* style)
{
    // FIXME: This could use m_owningLayer.transform(), but that currently has transform-origin
    // baked into it, and we don't want that.
    TransformationMatrix t;
    if (m_owningLayer.hasTransform()) {
        style->applyTransform(t, toRenderBox(renderer()).pixelSnappedBorderBoxRect().size(), RenderStyle::ExcludeTransformOrigin);
        makeMatrixRenderable(t, compositor().canRender3DTransforms());
    }
    
    if (m_contentsContainmentLayer) {
        m_contentsContainmentLayer->setTransform(t);
        m_graphicsLayer->setTransform(TransformationMatrix());
    } else
        m_graphicsLayer->setTransform(t);
}

#if ENABLE(CSS_FILTERS)
void RenderLayerBacking::updateFilters(const RenderStyle* style)
{
    m_canCompositeFilters = m_graphicsLayer->setFilters(owningLayer().computeFilterOperations(style));
}
#endif

#if ENABLE(CSS_COMPOSITING)
void RenderLayerBacking::updateLayerBlendMode(const RenderStyle*)
{
}
#endif

static bool hasNonZeroTransformOrigin(const RenderObject& renderer)
{
    const RenderStyle& style = renderer.style();
    return (style.transformOriginX().type() == Fixed && style.transformOriginX().value())
        || (style.transformOriginY().type() == Fixed && style.transformOriginY().value());
}

static bool layerOrAncestorIsTransformedOrUsingCompositedScrolling(RenderLayer& layer)
{
    for (RenderLayer* curr = &layer; curr; curr = curr->parent()) {
        if (curr->hasTransform() || curr->needsCompositedScrolling())
            return true;
    }
    
    return false;
}

bool RenderLayerBacking::shouldClipCompositedBounds() const
{
    // Scrollbar layers use this layer for relative positioning, so don't clip.
    if (layerForHorizontalScrollbar() || layerForVerticalScrollbar())
        return false;

    if (m_usingTiledCacheLayer)
        return false;

    if (layerOrAncestorIsTransformedOrUsingCompositedScrolling(m_owningLayer))
        return false;

    if (m_owningLayer.isFlowThreadCollectingGraphicsLayersUnderRegions())
        return false;

    return true;
}

void RenderLayerBacking::updateCompositedBounds()
{
    LayoutRect layerBounds = compositor().calculateCompositedBounds(m_owningLayer, m_owningLayer);

    // Clip to the size of the document or enclosing overflow-scroll layer.
    // If this or an ancestor is transformed, we can't currently compute the correct rect to intersect with.
    // We'd need RenderObject::convertContainerToLocalQuad(), which doesn't yet exist.
    if (shouldClipCompositedBounds()) {
        RenderView& view = m_owningLayer.renderer().view();
        RenderLayer* rootLayer = view.layer();

        LayoutRect clippingBounds;
        if (renderer().style().position() == FixedPosition && renderer().container() == &view)
            clippingBounds = view.frameView().viewportConstrainedVisibleContentRect();
        else
            clippingBounds = view.unscaledDocumentRect();

        if (&m_owningLayer != rootLayer)
            clippingBounds.intersect(m_owningLayer.backgroundClipRect(RenderLayer::ClipRectsContext(rootLayer, 0, AbsoluteClipRects)).rect()); // FIXME: Incorrect for CSS regions.

        LayoutPoint delta;
        m_owningLayer.convertToLayerCoords(rootLayer, delta, RenderLayer::AdjustForColumns);
        clippingBounds.move(-delta.x(), -delta.y());

        layerBounds.intersect(clippingBounds);
    }
    
    // If the element has a transform-origin that has fixed lengths, and the renderer has zero size,
    // then we need to ensure that the compositing layer has non-zero size so that we can apply
    // the transform-origin via the GraphicsLayer anchorPoint (which is expressed as a fractional value).
    if (layerBounds.isEmpty() && hasNonZeroTransformOrigin(renderer())) {
        layerBounds.setWidth(1);
        layerBounds.setHeight(1);
        m_artificiallyInflatedBounds = true;
    } else
        m_artificiallyInflatedBounds = false;

    setCompositedBounds(layerBounds);
}

void RenderLayerBacking::updateAfterWidgetResize()
{
    if (!renderer().isWidget())
        return;
    if (RenderLayerCompositor* innerCompositor = RenderLayerCompositor::frameContentsCompositor(toRenderWidget(&renderer()))) {
        innerCompositor->frameViewDidChangeSize();
        innerCompositor->frameViewDidChangeLocation(flooredIntPoint(contentsBox().location()));
    }
}

void RenderLayerBacking::updateAfterLayout(UpdateAfterLayoutFlags flags)
{
    if (!compositor().compositingLayersNeedRebuild()) {
        // Calling updateGraphicsLayerGeometry() here gives incorrect results, because the
        // position of this layer's GraphicsLayer depends on the position of our compositing
        // ancestor's GraphicsLayer. That cannot be determined until all the descendant 
        // RenderLayers of that ancestor have been processed via updateLayerPositions().
        //
        // The solution is to update compositing children of this layer here,
        // via updateCompositingChildrenGeometry().
        updateCompositedBounds();
        compositor().updateCompositingDescendantGeometry(m_owningLayer, m_owningLayer, flags & CompositingChildrenOnly);
        
        if (flags & IsUpdateRoot) {
            updateGraphicsLayerGeometry();
            compositor().updateRootLayerPosition();
            RenderLayer* stackingContainer = m_owningLayer.enclosingStackingContainer();
            if (!compositor().compositingLayersNeedRebuild() && stackingContainer && (stackingContainer != &m_owningLayer))
                compositor().updateCompositingDescendantGeometry(*stackingContainer, *stackingContainer, flags & CompositingChildrenOnly);
        }
    }
    
    if (flags & NeedsFullRepaint && !paintsIntoWindow() && !paintsIntoCompositedAncestor())
        setContentsNeedDisplay();
}

bool RenderLayerBacking::updateGraphicsLayerConfiguration()
{
    m_owningLayer.updateDescendantDependentFlags();
    m_owningLayer.updateZOrderLists();

    bool layerConfigChanged = false;
    setBackgroundLayerPaintsFixedRootBackground(compositor().needsFixedRootBackgroundLayer(m_owningLayer));
    
    // The background layer is currently only used for fixed root backgrounds.
    if (updateBackgroundLayer(m_backgroundLayerPaintsFixedRootBackground))
        layerConfigChanged = true;

    if (updateForegroundLayer(compositor().needsContentsCompositingLayer(m_owningLayer)))
        layerConfigChanged = true;
    
    bool needsDescendentsClippingLayer = compositor().clipsCompositingDescendants(m_owningLayer);

    // Our scrolling layer will clip.
    if (m_owningLayer.needsCompositedScrolling())
        needsDescendentsClippingLayer = false;

    if (updateAncestorClippingLayer(compositor().clippedByAncestor(m_owningLayer)))
        layerConfigChanged = true;

    if (updateDescendantClippingLayer(needsDescendentsClippingLayer))
        layerConfigChanged = true;

    if (updateOverflowControlsLayers(requiresHorizontalScrollbarLayer(), requiresVerticalScrollbarLayer(), requiresScrollCornerLayer()))
        layerConfigChanged = true;

    if (updateScrollingLayers(m_owningLayer.needsCompositedScrolling()))
        layerConfigChanged = true;

    if (layerConfigChanged)
        updateInternalHierarchy();

    if (GraphicsLayer* flatteningLayer = tileCacheFlatteningLayer()) {
        if (layerConfigChanged || flatteningLayer->parent() != m_graphicsLayer.get())
            m_graphicsLayer->addChild(flatteningLayer);
    }

    if (updateMaskLayer(renderer().hasMask()))
        m_graphicsLayer->setMaskLayer(m_maskLayer.get());

    if (m_owningLayer.hasReflection()) {
        if (m_owningLayer.reflectionLayer()->backing()) {
            GraphicsLayer* reflectionLayer = m_owningLayer.reflectionLayer()->backing()->graphicsLayer();
            m_graphicsLayer->setReplicatedByLayer(reflectionLayer);
        }
    } else
        m_graphicsLayer->setReplicatedByLayer(0);

    bool isSimpleContainer = isSimpleContainerCompositingLayer();
    bool didUpdateContentsRect = false;
    updateDirectlyCompositedContents(isSimpleContainer, didUpdateContentsRect);

    updateRootLayerConfiguration();
    
    if (isDirectlyCompositedImage())
        updateImageContents();

    if (renderer().isEmbeddedObject() && toRenderEmbeddedObject(&renderer())->allowsAcceleratedCompositing()) {
        PluginViewBase* pluginViewBase = toPluginViewBase(toRenderWidget(&renderer())->widget());
        if (!pluginViewBase->shouldNotAddLayer())
            m_graphicsLayer->setContentsToMedia(pluginViewBase->platformLayer());
    }
#if ENABLE(VIDEO)
    else if (renderer().isVideo()) {
        HTMLMediaElement* mediaElement = toHTMLMediaElement(renderer().element());
        m_graphicsLayer->setContentsToMedia(mediaElement->platformLayer());
    }
#endif
#if ENABLE(WEBGL) || ENABLE(ACCELERATED_2D_CANVAS)
    else if (isAcceleratedCanvas(&renderer())) {
        const HTMLCanvasElement* canvas = toHTMLCanvasElement(renderer().element());
        if (CanvasRenderingContext* context = canvas->renderingContext())
            m_graphicsLayer->setContentsToCanvas(context->platformLayer());
        layerConfigChanged = true;
    }
#endif
    if (renderer().isWidget())
        layerConfigChanged = RenderLayerCompositor::parentFrameContentLayers(toRenderWidget(&renderer()));

    return layerConfigChanged;
}

static IntRect clipBox(RenderBox& renderer)
{
    LayoutRect result = PaintInfo::infiniteRect();
    if (renderer.hasOverflowClip())
        result = renderer.overflowClipRect(LayoutPoint(), 0); // FIXME: Incorrect for CSS regions.

    if (renderer.hasClip())
        result.intersect(renderer.clipRect(LayoutPoint(), 0)); // FIXME: Incorrect for CSS regions.

    return pixelSnappedIntRect(result);
}

void RenderLayerBacking::updateGraphicsLayerGeometry()
{
    // If we haven't built z-order lists yet, wait until later.
    if (m_owningLayer.isStackingContainer() && m_owningLayer.m_zOrderListsDirty)
        return;

    // Set transform property, if it is not animating. We have to do this here because the transform
    // is affected by the layer dimensions.
    if (!renderer().animation().isRunningAcceleratedAnimationOnRenderer(&renderer(), CSSPropertyWebkitTransform))
        updateTransform(&renderer().style());

    // Set opacity, if it is not animating.
    if (!renderer().animation().isRunningAcceleratedAnimationOnRenderer(&renderer(), CSSPropertyOpacity))
        updateOpacity(&renderer().style());
        
#if ENABLE(CSS_FILTERS)
    updateFilters(&renderer().style());
#endif

#if ENABLE(CSS_COMPOSITING)
    updateLayerBlendMode(&renderer().style());
#endif

    bool isSimpleContainer = isSimpleContainerCompositingLayer();
    
    m_owningLayer.updateDescendantDependentFlags();

    // m_graphicsLayer is the corresponding GraphicsLayer for this RenderLayer and its non-compositing
    // descendants. So, the visibility flag for m_graphicsLayer should be true if there are any
    // non-compositing visible layers.
    m_graphicsLayer->setContentsVisible(m_owningLayer.hasVisibleContent() || hasVisibleNonCompositingDescendantLayers());

    const RenderStyle& style = renderer().style();
    // FIXME: reflections should force transform-style to be flat in the style: https://bugs.webkit.org/show_bug.cgi?id=106959
    bool preserves3D = style.transformStyle3D() == TransformStyle3DPreserve3D && !renderer().hasReflection();
    m_graphicsLayer->setPreserves3D(preserves3D);
    m_graphicsLayer->setBackfaceVisibility(style.backfaceVisibility() == BackfaceVisibilityVisible);

    RenderLayer* compAncestor = m_owningLayer.ancestorCompositingLayer();
    
    // We compute everything relative to the enclosing compositing layer.
    IntRect ancestorCompositingBounds;
    if (compAncestor) {
        ASSERT(compAncestor->backing());
        ancestorCompositingBounds = pixelSnappedIntRect(compAncestor->backing()->compositedBounds());
    }

    LayoutRect localRawCompositingBounds = compositedBounds();
    LayoutPoint rawDelta;
    m_owningLayer.convertToLayerCoords(compAncestor, rawDelta, RenderLayer::AdjustForColumns);
    IntPoint delta = flooredIntPoint(rawDelta);
    m_subpixelAccumulation = toLayoutSize(rawDelta.fraction());
    // Move the bounds by the subpixel accumulation so that it pixel-snaps relative to absolute pixels instead of local coordinates.
    localRawCompositingBounds.move(m_subpixelAccumulation);

    IntRect localCompositingBounds = pixelSnappedIntRect(localRawCompositingBounds);
    IntRect relativeCompositingBounds(localCompositingBounds);
    relativeCompositingBounds.moveBy(delta);

    adjustAncestorCompositingBoundsForFlowThread(ancestorCompositingBounds, compAncestor);

    IntPoint graphicsLayerParentLocation;
    if (compAncestor && compAncestor->backing()->hasClippingLayer()) {
        // If the compositing ancestor has a layer to clip children, we parent in that, and therefore
        // position relative to it.
        IntRect clippingBox = clipBox(toRenderBox(compAncestor->renderer()));
        graphicsLayerParentLocation = clippingBox.location();
    } else if (compAncestor)
        graphicsLayerParentLocation = ancestorCompositingBounds.location();
    else
        graphicsLayerParentLocation = renderer().view().documentRect().location();

    if (compAncestor && compAncestor->needsCompositedScrolling()) {
        RenderBox& renderBox = toRenderBox(compAncestor->renderer());
        IntSize scrollOffset = compAncestor->scrolledContentOffset();
        IntPoint scrollOrigin(renderBox.borderLeft(), renderBox.borderTop());
        graphicsLayerParentLocation = scrollOrigin - scrollOffset;
    }
    
    if (compAncestor && m_ancestorClippingLayer) {
        // Call calculateRects to get the backgroundRect which is what is used to clip the contents of this
        // layer. Note that we call it with temporaryClipRects = true because normally when computing clip rects
        // for a compositing layer, rootLayer is the layer itself.
        RenderLayer::ClipRectsContext clipRectsContext(compAncestor, 0, TemporaryClipRects, IgnoreOverlayScrollbarSize, IgnoreOverflowClip);
        IntRect parentClipRect = pixelSnappedIntRect(m_owningLayer.backgroundClipRect(clipRectsContext).rect()); // FIXME: Incorrect for CSS regions.
        ASSERT(parentClipRect != PaintInfo::infiniteRect());
        m_ancestorClippingLayer->setPosition(FloatPoint(parentClipRect.location() - graphicsLayerParentLocation));
        m_ancestorClippingLayer->setSize(parentClipRect.size());

        // backgroundRect is relative to compAncestor, so subtract deltaX/deltaY to get back to local coords.
        m_ancestorClippingLayer->setOffsetFromRenderer(parentClipRect.location() - delta);

        // The primary layer is then parented in, and positioned relative to this clipping layer.
        graphicsLayerParentLocation = parentClipRect.location();
    }

    FloatSize contentsSize = relativeCompositingBounds.size();
    
    if (m_contentsContainmentLayer) {
        m_contentsContainmentLayer->setPreserves3D(preserves3D);
        m_contentsContainmentLayer->setPosition(FloatPoint(relativeCompositingBounds.location() - graphicsLayerParentLocation));
        // Use the same size as m_graphicsLayer so transforms behave correctly.
        m_contentsContainmentLayer->setSize(contentsSize);
        graphicsLayerParentLocation = relativeCompositingBounds.location();
    }

    m_graphicsLayer->setPosition(FloatPoint(relativeCompositingBounds.location() - graphicsLayerParentLocation));
    m_graphicsLayer->setSize(contentsSize);
    m_graphicsLayer->setOffsetFromRenderer(toIntSize(localCompositingBounds.location()));

    if (!m_isMainFrameRenderViewLayer) {
        // For non-root layers, background is always painted by the primary graphics layer.
        ASSERT(!m_backgroundLayer);
        m_graphicsLayer->setContentsOpaque(m_owningLayer.backgroundIsKnownToBeOpaqueInRect(localCompositingBounds));
    }

    // If we have a layer that clips children, position it.
    IntRect clippingBox;
    if (GraphicsLayer* clipLayer = clippingLayer()) {
        clippingBox = clipBox(toRenderBox(renderer()));
        clipLayer->setPosition(FloatPoint(clippingBox.location() - localCompositingBounds.location()));
        clipLayer->setSize(clippingBox.size());
        clipLayer->setOffsetFromRenderer(toIntSize(clippingBox.location()));
    }
    
    if (m_maskLayer) {
        m_maskLayer->setSize(m_graphicsLayer->size());
        m_maskLayer->setPosition(FloatPoint());
        m_maskLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
    }
    
    if (m_owningLayer.hasTransform()) {
        const IntRect borderBox = toRenderBox(renderer()).pixelSnappedBorderBoxRect();

        // Get layout bounds in the coords of compAncestor to match relativeCompositingBounds.
        IntRect layerBounds(delta, borderBox.size());

        // Update properties that depend on layer dimensions
        FloatPoint3D transformOrigin = computeTransformOrigin(borderBox);
        // Compute the anchor point, which is in the center of the renderer box unless transform-origin is set.
        FloatPoint3D anchor(relativeCompositingBounds.width()  != 0.0f ? ((layerBounds.x() - relativeCompositingBounds.x()) + transformOrigin.x()) / relativeCompositingBounds.width()  : 0.5f,
                            relativeCompositingBounds.height() != 0.0f ? ((layerBounds.y() - relativeCompositingBounds.y()) + transformOrigin.y()) / relativeCompositingBounds.height() : 0.5f,
                            transformOrigin.z());
        if (m_contentsContainmentLayer)
            m_contentsContainmentLayer->setAnchorPoint(anchor);
        else
            m_graphicsLayer->setAnchorPoint(anchor);

        const RenderStyle& style = renderer().style();
        GraphicsLayer* clipLayer = clippingLayer();
        if (style.hasPerspective()) {
            TransformationMatrix t = owningLayer().perspectiveTransform();
            
            if (clipLayer) {
                clipLayer->setChildrenTransform(t);
                m_graphicsLayer->setChildrenTransform(TransformationMatrix());
            }
            else
                m_graphicsLayer->setChildrenTransform(t);
        } else {
            if (clipLayer)
                clipLayer->setChildrenTransform(TransformationMatrix());
            else
                m_graphicsLayer->setChildrenTransform(TransformationMatrix());
        }
    } else {
        m_graphicsLayer->setAnchorPoint(FloatPoint3D(0.5f, 0.5f, 0));
        if (m_contentsContainmentLayer)
            m_contentsContainmentLayer->setAnchorPoint(FloatPoint3D(0.5f, 0.5f, 0));
    }

    if (m_foregroundLayer) {
        FloatPoint foregroundPosition;
        FloatSize foregroundSize = contentsSize;
        IntSize foregroundOffset = m_graphicsLayer->offsetFromRenderer();
        if (hasClippingLayer()) {
            // If we have a clipping layer (which clips descendants), then the foreground layer is a child of it,
            // so that it gets correctly sorted with children. In that case, position relative to the clipping layer.
            foregroundSize = FloatSize(clippingBox.size());
            foregroundOffset = toIntSize(clippingBox.location());
        }

        m_foregroundLayer->setPosition(foregroundPosition);
        m_foregroundLayer->setSize(foregroundSize);
        m_foregroundLayer->setOffsetFromRenderer(foregroundOffset);
    }

    if (m_backgroundLayer) {
        FloatPoint backgroundPosition;
        FloatSize backgroundSize = contentsSize;
        if (backgroundLayerPaintsFixedRootBackground()) {
            const FrameView& frameView = renderer().view().frameView();
            backgroundPosition = IntPoint(frameView.scrollOffsetForFixedPosition());
            backgroundSize = frameView.visibleContentRect().size();
        }
        m_backgroundLayer->setPosition(backgroundPosition);
        m_backgroundLayer->setSize(backgroundSize);
        m_backgroundLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
    }

    if (m_owningLayer.reflectionLayer() && m_owningLayer.reflectionLayer()->isComposited()) {
        RenderLayerBacking* reflectionBacking = m_owningLayer.reflectionLayer()->backing();
        reflectionBacking->updateGraphicsLayerGeometry();
        
        // The reflection layer has the bounds of m_owningLayer.reflectionLayer(),
        // but the reflected layer is the bounds of this layer, so we need to position it appropriately.
        FloatRect layerBounds = compositedBounds();
        FloatRect reflectionLayerBounds = reflectionBacking->compositedBounds();
        reflectionBacking->graphicsLayer()->setReplicatedLayerPosition(FloatPoint(layerBounds.location() - reflectionLayerBounds.location()));
    }

    if (m_scrollingLayer) {
        ASSERT(m_scrollingContentsLayer);
        RenderBox& renderBox = toRenderBox(renderer());
        IntRect paddingBox(renderBox.borderLeft(), renderBox.borderTop(), renderBox.width() - renderBox.borderLeft() - renderBox.borderRight(), renderBox.height() - renderBox.borderTop() - renderBox.borderBottom());
        IntSize scrollOffset = m_owningLayer.scrollOffset();

        m_scrollingLayer->setPosition(FloatPoint(paddingBox.location() - localCompositingBounds.location()));

        m_scrollingLayer->setSize(paddingBox.size());
        m_scrollingContentsLayer->setPosition(FloatPoint(-scrollOffset.width(), -scrollOffset.height()));

        IntSize oldScrollingLayerOffset = m_scrollingLayer->offsetFromRenderer();
        m_scrollingLayer->setOffsetFromRenderer(-toIntSize(paddingBox.location()));

        bool paddingBoxOffsetChanged = oldScrollingLayerOffset != m_scrollingLayer->offsetFromRenderer();

        IntSize scrollSize(m_owningLayer.scrollWidth(), m_owningLayer.scrollHeight());
        if (scrollSize != m_scrollingContentsLayer->size() || paddingBoxOffsetChanged)
            m_scrollingContentsLayer->setNeedsDisplay();

        IntSize scrollingContentsOffset = toIntSize(paddingBox.location() - scrollOffset);
        if (scrollingContentsOffset != m_scrollingContentsLayer->offsetFromRenderer() || scrollSize != m_scrollingContentsLayer->size())
            compositor().scrollingLayerDidChange(m_owningLayer);

        m_scrollingContentsLayer->setSize(scrollSize);
        // FIXME: The paint offset and the scroll offset should really be separate concepts.
        m_scrollingContentsLayer->setOffsetFromRenderer(scrollingContentsOffset, GraphicsLayer::DontSetNeedsDisplay);

        if (m_foregroundLayer) {
            m_foregroundLayer->setSize(m_scrollingContentsLayer->size());
            m_foregroundLayer->setOffsetFromRenderer(m_scrollingContentsLayer->offsetFromRenderer());
        }
    }

    // If this layer was created just for clipping or to apply perspective, it doesn't need its own backing store.
    setRequiresOwnBackingStore(compositor().requiresOwnBackingStore(m_owningLayer, compAncestor, relativeCompositingBounds, ancestorCompositingBounds));

    bool didUpdateContentsRect = false;
    updateDirectlyCompositedContents(isSimpleContainer, didUpdateContentsRect);
    if (!didUpdateContentsRect && m_graphicsLayer->hasContentsLayer())
        resetContentsRect();

    updateDrawsContent(isSimpleContainer);
    updateAfterWidgetResize();
    registerScrollingLayers();
}

void RenderLayerBacking::adjustAncestorCompositingBoundsForFlowThread(IntRect& ancestorCompositingBounds, const RenderLayer* compositingAncestor) const
{
    if (!m_owningLayer.isInsideFlowThread())
        return;

    RenderLayer* flowThreadLayer = m_owningLayer.isInsideOutOfFlowThread() ? m_owningLayer.stackingContainer() : m_owningLayer.enclosingFlowThreadAncestor();
    if (flowThreadLayer && flowThreadLayer->isRenderFlowThread()) {
        RenderFlowThread& flowThread = toRenderFlowThread(flowThreadLayer->renderer());
        if (m_owningLayer.isFlowThreadCollectingGraphicsLayersUnderRegions()) {
            // The RenderNamedFlowThread is not composited, as we need it to paint the 
            // background layer of the regions. We need to compensate for that by manually
            // subtracting the position of the flow-thread.
            IntPoint flowPosition;
            flowThreadLayer->convertToPixelSnappedLayerCoords(compositingAncestor, flowPosition);
            ancestorCompositingBounds.moveBy(flowPosition);
        }

        // Move the ancestor position at the top of the region where the composited layer is going to display.
        RenderNamedFlowFragment* parentRegion = flowThread.cachedRegionForCompositedLayer(m_owningLayer);
        if (parentRegion) {
            IntPoint flowDelta;
            m_owningLayer.convertToPixelSnappedLayerCoords(flowThreadLayer, flowDelta);
            parentRegion->adjustRegionBoundsFromFlowThreadPortionRect(flowDelta, ancestorCompositingBounds);
            RenderBoxModelObject* layerOwner = toRenderBoxModelObject(parentRegion->layerOwner());
            if (layerOwner->hasLayer() && layerOwner->layer()->backing()) {
                // Make sure that the region propagates its borders, paddings, outlines or box-shadows to layers inside it.
                // Note that the composited bounds of the RenderRegion are already calculated
                // because RenderLayerCompositor::rebuildCompositingLayerTree will only
                // iterate on the content of the region after the region itself is computed.
                ancestorCompositingBounds.moveBy(roundedIntPoint(layerOwner->layer()->backing()->compositedBounds().location()));
                ancestorCompositingBounds.move(-layerOwner->borderAndPaddingStart(), -layerOwner->borderAndPaddingBefore());
            }
        }
    }
}

void RenderLayerBacking::updateDirectlyCompositedContents(bool isSimpleContainer, bool& didUpdateContentsRect)
{
    if (!m_owningLayer.hasVisibleContent())
        return;

    // The order of operations here matters, since the last valid type of contents needs
    // to also update the contentsRect.
    updateDirectlyCompositedBackgroundColor(isSimpleContainer, didUpdateContentsRect);
    updateDirectlyCompositedBackgroundImage(isSimpleContainer, didUpdateContentsRect);
}

void RenderLayerBacking::registerScrollingLayers()
{
    // Register fixed position layers and their containers with the scrolling coordinator.
    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);
    if (!scrollingCoordinator)
        return;

    compositor().updateViewportConstraintStatus(m_owningLayer);

    if (!scrollingCoordinator->supportsFixedPositionLayers())
        return;

    // Page scale is applied as a transform on the root render view layer. Because the scroll
    // layer is further up in the hierarchy, we need to avoid marking the root render view
    // layer as a container.
    bool isContainer = m_owningLayer.hasTransform() && !m_owningLayer.isRootLayer();
    scrollingCoordinator->setLayerIsContainerForFixedPositionLayers(childForSuperlayers(), isContainer);
}

void RenderLayerBacking::updateInternalHierarchy()
{
    // m_foregroundLayer has to be inserted in the correct order with child layers,
    // so it's not inserted here.
    if (m_ancestorClippingLayer)
        m_ancestorClippingLayer->removeAllChildren();
    
    if (m_contentsContainmentLayer) {
        m_contentsContainmentLayer->removeAllChildren();
        if (m_ancestorClippingLayer)
            m_ancestorClippingLayer->addChild(m_contentsContainmentLayer.get());
    }
    
    if (m_backgroundLayer)
        m_contentsContainmentLayer->addChild(m_backgroundLayer.get());

    if (m_contentsContainmentLayer)
        m_contentsContainmentLayer->addChild(m_graphicsLayer.get());
    else if (m_ancestorClippingLayer)
        m_ancestorClippingLayer->addChild(m_graphicsLayer.get());

    if (m_childContainmentLayer) {
        m_childContainmentLayer->removeFromParent();
        m_graphicsLayer->addChild(m_childContainmentLayer.get());
    }

    if (m_scrollingLayer) {
        GraphicsLayer* superlayer = m_childContainmentLayer ? m_childContainmentLayer.get() : m_graphicsLayer.get();
        m_scrollingLayer->removeFromParent();
        superlayer->addChild(m_scrollingLayer.get());
    }

    // The clip for child layers does not include space for overflow controls, so they exist as
    // siblings of the clipping layer if we have one. Normal children of this layer are set as
    // children of the clipping layer.
    if (m_layerForHorizontalScrollbar) {
        m_layerForHorizontalScrollbar->removeFromParent();
        m_graphicsLayer->addChild(m_layerForHorizontalScrollbar.get());
    }
    if (m_layerForVerticalScrollbar) {
        m_layerForVerticalScrollbar->removeFromParent();
        m_graphicsLayer->addChild(m_layerForVerticalScrollbar.get());
    }
    if (m_layerForScrollCorner) {
        m_layerForScrollCorner->removeFromParent();
        m_graphicsLayer->addChild(m_layerForScrollCorner.get());
    }
}

void RenderLayerBacking::resetContentsRect()
{
    m_graphicsLayer->setContentsRect(pixelSnappedIntRect(contentsBox()));
    
    LayoutRect contentsClippingRect;
    if (renderer().isBox())
        contentsClippingRect = toRenderBox(renderer()).contentBoxRect();

    contentsClippingRect.move(contentOffsetInCompostingLayer());
    m_graphicsLayer->setContentsClippingRect(pixelSnappedIntRect(contentsClippingRect));

    m_graphicsLayer->setContentsTileSize(IntSize());
    m_graphicsLayer->setContentsTilePhase(IntPoint());
}

void RenderLayerBacking::updateDrawsContent()
{
    updateDrawsContent(isSimpleContainerCompositingLayer());
}

void RenderLayerBacking::updateDrawsContent(bool isSimpleContainer)
{
    if (m_scrollingLayer) {
        // We don't have to consider overflow controls, because we know that the scrollbars are drawn elsewhere.
        // m_graphicsLayer only needs backing store if the non-scrolling parts (background, outlines, borders, shadows etc) need to paint.
        // m_scrollingLayer never has backing store.
        // m_scrollingContentsLayer only needs backing store if the scrolled contents need to paint.
        bool hasNonScrollingPaintedContent = m_owningLayer.hasVisibleContent() && m_owningLayer.hasBoxDecorationsOrBackground();
        m_graphicsLayer->setDrawsContent(hasNonScrollingPaintedContent);

        bool hasScrollingPaintedContent = m_owningLayer.hasVisibleContent() && (renderer().hasBackground() || paintsChildren());
        m_scrollingContentsLayer->setDrawsContent(hasScrollingPaintedContent);
        return;
    }

    bool hasPaintedContent = containsPaintedContent(isSimpleContainer);

    // FIXME: we could refine this to only allocate backing for one of these layers if possible.
    m_graphicsLayer->setDrawsContent(hasPaintedContent);
    if (m_foregroundLayer)
        m_foregroundLayer->setDrawsContent(hasPaintedContent);

    if (m_backgroundLayer)
        m_backgroundLayer->setDrawsContent(hasPaintedContent);
}

// Return true if the layer changed.
bool RenderLayerBacking::updateAncestorClippingLayer(bool needsAncestorClip)
{
    bool layersChanged = false;

    if (needsAncestorClip) {
        if (!m_ancestorClippingLayer) {
            m_ancestorClippingLayer = createGraphicsLayer("Ancestor clipping Layer");
            m_ancestorClippingLayer->setMasksToBounds(true);
            layersChanged = true;
        }
    } else if (hasAncestorClippingLayer()) {
        willDestroyLayer(m_ancestorClippingLayer.get());
        m_ancestorClippingLayer->removeFromParent();
        m_ancestorClippingLayer = nullptr;
        layersChanged = true;
    }
    
    return layersChanged;
}

// Return true if the layer changed.
bool RenderLayerBacking::updateDescendantClippingLayer(bool needsDescendantClip)
{
    bool layersChanged = false;

    if (needsDescendantClip) {
        if (!m_childContainmentLayer && !m_usingTiledCacheLayer) {
            m_childContainmentLayer = createGraphicsLayer("Child clipping Layer");
            m_childContainmentLayer->setMasksToBounds(true);
            layersChanged = true;
        }
    } else if (hasClippingLayer()) {
        willDestroyLayer(m_childContainmentLayer.get());
        m_childContainmentLayer->removeFromParent();
        m_childContainmentLayer = nullptr;
        layersChanged = true;
    }
    
    return layersChanged;
}

void RenderLayerBacking::setBackgroundLayerPaintsFixedRootBackground(bool backgroundLayerPaintsFixedRootBackground)
{
    m_backgroundLayerPaintsFixedRootBackground = backgroundLayerPaintsFixedRootBackground;
}

bool RenderLayerBacking::requiresHorizontalScrollbarLayer() const
{
    if (!m_owningLayer.hasOverlayScrollbars() && !m_owningLayer.needsCompositedScrolling())
        return false;
    return m_owningLayer.horizontalScrollbar();
}

bool RenderLayerBacking::requiresVerticalScrollbarLayer() const
{
    if (!m_owningLayer.hasOverlayScrollbars() && !m_owningLayer.needsCompositedScrolling())
        return false;
    return m_owningLayer.verticalScrollbar();
}

bool RenderLayerBacking::requiresScrollCornerLayer() const
{
    if (!m_owningLayer.hasOverlayScrollbars() && !m_owningLayer.needsCompositedScrolling())
        return false;
    return !m_owningLayer.scrollCornerAndResizerRect().isEmpty();
}

bool RenderLayerBacking::updateOverflowControlsLayers(bool needsHorizontalScrollbarLayer, bool needsVerticalScrollbarLayer, bool needsScrollCornerLayer)
{
    bool horizontalScrollbarLayerChanged = false;
    if (needsHorizontalScrollbarLayer) {
        if (!m_layerForHorizontalScrollbar) {
            m_layerForHorizontalScrollbar = createGraphicsLayer("horizontal scrollbar");
            horizontalScrollbarLayerChanged = true;
        }
    } else if (m_layerForHorizontalScrollbar) {
        willDestroyLayer(m_layerForHorizontalScrollbar.get());
        m_layerForHorizontalScrollbar = nullptr;
        horizontalScrollbarLayerChanged = true;
    }

    bool verticalScrollbarLayerChanged = false;
    if (needsVerticalScrollbarLayer) {
        if (!m_layerForVerticalScrollbar) {
            m_layerForVerticalScrollbar = createGraphicsLayer("vertical scrollbar");
            verticalScrollbarLayerChanged = true;
        }
    } else if (m_layerForVerticalScrollbar) {
        willDestroyLayer(m_layerForVerticalScrollbar.get());
        m_layerForVerticalScrollbar = nullptr;
        verticalScrollbarLayerChanged = true;
    }

    bool scrollCornerLayerChanged = false;
    if (needsScrollCornerLayer) {
        if (!m_layerForScrollCorner) {
            m_layerForScrollCorner = createGraphicsLayer("scroll corner");
            scrollCornerLayerChanged = true;
        }
    } else if (m_layerForScrollCorner) {
        willDestroyLayer(m_layerForScrollCorner.get());
        m_layerForScrollCorner = nullptr;
        scrollCornerLayerChanged = true;
    }

    if (ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer)) {
        if (horizontalScrollbarLayerChanged)
            scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(&m_owningLayer, HorizontalScrollbar);
        if (verticalScrollbarLayerChanged)
            scrollingCoordinator->scrollableAreaScrollbarLayerDidChange(&m_owningLayer, VerticalScrollbar);
    }

    return horizontalScrollbarLayerChanged || verticalScrollbarLayerChanged || scrollCornerLayerChanged;
}

void RenderLayerBacking::positionOverflowControlsLayers(const IntSize& offsetFromRoot)
{
    IntSize offsetFromRenderer = m_graphicsLayer->offsetFromRenderer();
    if (GraphicsLayer* layer = layerForHorizontalScrollbar()) {
        Scrollbar* hBar = m_owningLayer.horizontalScrollbar();
        if (hBar) {
            layer->setPosition(hBar->frameRect().location() - offsetFromRoot - offsetFromRenderer);
            layer->setSize(hBar->frameRect().size());
            if (layer->hasContentsLayer()) {
                IntRect barRect = IntRect(IntPoint(), hBar->frameRect().size());
                layer->setContentsRect(barRect);
                layer->setContentsClippingRect(barRect);
            }
        }
        layer->setDrawsContent(hBar && !layer->hasContentsLayer());
    }
    
    if (GraphicsLayer* layer = layerForVerticalScrollbar()) {
        Scrollbar* vBar = m_owningLayer.verticalScrollbar();
        if (vBar) {
            layer->setPosition(vBar->frameRect().location() - offsetFromRoot - offsetFromRenderer);
            layer->setSize(vBar->frameRect().size());
            if (layer->hasContentsLayer()) {
                IntRect barRect = IntRect(IntPoint(), vBar->frameRect().size());
                layer->setContentsRect(barRect);
                layer->setContentsClippingRect(barRect);
            }
        }
        layer->setDrawsContent(vBar && !layer->hasContentsLayer());
    }

    if (GraphicsLayer* layer = layerForScrollCorner()) {
        const LayoutRect& scrollCornerAndResizer = m_owningLayer.scrollCornerAndResizerRect();
        layer->setPosition(scrollCornerAndResizer.location() - offsetFromRenderer);
        layer->setSize(scrollCornerAndResizer.size());
        layer->setDrawsContent(!scrollCornerAndResizer.isEmpty());
    }
}

bool RenderLayerBacking::hasUnpositionedOverflowControlsLayers() const
{
    if (GraphicsLayer* layer = layerForHorizontalScrollbar())
        if (!layer->drawsContent())
            return true;

    if (GraphicsLayer* layer = layerForVerticalScrollbar())
        if (!layer->drawsContent())
            return true;

    if (GraphicsLayer* layer = layerForScrollCorner())
        if (!layer->drawsContent())
            return true;

    return false;
}

bool RenderLayerBacking::updateForegroundLayer(bool needsForegroundLayer)
{
    bool layerChanged = false;
    if (needsForegroundLayer) {
        if (!m_foregroundLayer) {
            String layerName;
#ifndef NDEBUG
            layerName = m_owningLayer.name() + " (foreground)";
#endif
            m_foregroundLayer = createGraphicsLayer(layerName);
            m_foregroundLayer->setDrawsContent(true);
            m_foregroundLayer->setPaintingPhase(GraphicsLayerPaintForeground);
            layerChanged = true;
        }
    } else if (m_foregroundLayer) {
        willDestroyLayer(m_foregroundLayer.get());
        m_foregroundLayer->removeFromParent();
        m_foregroundLayer = nullptr;
        layerChanged = true;
    }

    if (layerChanged) {
        m_graphicsLayer->setNeedsDisplay();
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());
    }

    return layerChanged;
}

bool RenderLayerBacking::updateBackgroundLayer(bool needsBackgroundLayer)
{
    bool layerChanged = false;
    if (needsBackgroundLayer) {
        if (!m_backgroundLayer) {
            String layerName;
#ifndef NDEBUG
            layerName = m_owningLayer.name() + " (background)";
#endif
            m_backgroundLayer = createGraphicsLayer(layerName);
            m_backgroundLayer->setDrawsContent(true);
            m_backgroundLayer->setAnchorPoint(FloatPoint3D());
            m_backgroundLayer->setPaintingPhase(GraphicsLayerPaintBackground);
            layerChanged = true;
        }
        
        if (!m_contentsContainmentLayer) {
            String layerName;
#ifndef NDEBUG
            layerName = m_owningLayer.name() + " (contents containment)";
#endif
            m_contentsContainmentLayer = createGraphicsLayer(layerName);
            m_contentsContainmentLayer->setAppliesPageScale(true);
            m_graphicsLayer->setAppliesPageScale(false);
            layerChanged = true;
        }
    } else {
        if (m_backgroundLayer) {
            willDestroyLayer(m_backgroundLayer.get());
            m_backgroundLayer->removeFromParent();
            m_backgroundLayer = nullptr;
            layerChanged = true;
        }
        if (m_contentsContainmentLayer) {
            willDestroyLayer(m_contentsContainmentLayer.get());
            m_contentsContainmentLayer->removeFromParent();
            m_contentsContainmentLayer = nullptr;
            layerChanged = true;
            m_graphicsLayer->setAppliesPageScale(true);
        }
    }
    
    if (layerChanged) {
        m_graphicsLayer->setNeedsDisplay();
        // This assumes that the background layer is only used for fixed backgrounds, which is currently a correct assumption.
        compositor().fixedRootBackgroundLayerChanged();
    }
    
    return layerChanged;
}

bool RenderLayerBacking::updateMaskLayer(bool needsMaskLayer)
{
    bool layerChanged = false;
    if (needsMaskLayer) {
        if (!m_maskLayer) {
            m_maskLayer = createGraphicsLayer("Mask");
            m_maskLayer->setDrawsContent(true);
            m_maskLayer->setPaintingPhase(GraphicsLayerPaintMask);
            layerChanged = true;
        }
    } else if (m_maskLayer) {
        willDestroyLayer(m_maskLayer.get());
        m_maskLayer = nullptr;
        layerChanged = true;
    }

    if (layerChanged)
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());

    return layerChanged;
}

bool RenderLayerBacking::updateScrollingLayers(bool needsScrollingLayers)
{
    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);

    bool layerChanged = false;
    if (needsScrollingLayers) {
        if (!m_scrollingLayer) {
            // Outer layer which corresponds with the scroll view.
            m_scrollingLayer = createGraphicsLayer("Scrolling container");
            m_scrollingLayer->setDrawsContent(false);
            m_scrollingLayer->setMasksToBounds(true);

            // Inner layer which renders the content that scrolls.
            m_scrollingContentsLayer = createGraphicsLayer("Scrolled Contents");
            m_scrollingContentsLayer->setDrawsContent(true);
            GraphicsLayerPaintingPhase paintPhase = GraphicsLayerPaintOverflowContents | GraphicsLayerPaintCompositedScroll;
            if (!m_foregroundLayer)
                paintPhase |= GraphicsLayerPaintForeground;
            m_scrollingContentsLayer->setPaintingPhase(paintPhase);
            m_scrollingLayer->addChild(m_scrollingContentsLayer.get());

            layerChanged = true;
            if (scrollingCoordinator)
                scrollingCoordinator->scrollableAreaScrollLayerDidChange(&m_owningLayer);
        }
    } else if (m_scrollingLayer) {
        willDestroyLayer(m_scrollingLayer.get());
        willDestroyLayer(m_scrollingContentsLayer.get());
        m_scrollingLayer = nullptr;
        m_scrollingContentsLayer = nullptr;
        layerChanged = true;
        if (scrollingCoordinator)
            scrollingCoordinator->scrollableAreaScrollLayerDidChange(&m_owningLayer);
    }

    if (layerChanged) {
        updateInternalHierarchy();
        m_graphicsLayer->setPaintingPhase(paintingPhaseForPrimaryLayer());
        m_graphicsLayer->setNeedsDisplay();
        compositor().scrollingLayerDidChange(m_owningLayer);
    }

    return layerChanged;
}

void RenderLayerBacking::attachToScrollingCoordinatorWithParent(RenderLayerBacking* parent)
{
    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);
    if (!scrollingCoordinator)
        return;

    // FIXME: When we support overflow areas, we will have to refine this for overflow areas that are also
    // positon:fixed.
    ScrollingNodeType nodeType;
    if (renderer().style().position() == FixedPosition)
        nodeType = FixedNode;
    else if (renderer().style().position() == StickyPosition)
        nodeType = StickyNode;
    else
        nodeType = ScrollingNode;

    ScrollingNodeID parentID = parent ? parent->scrollLayerID() : 0;
    m_scrollLayerID = scrollingCoordinator->attachToStateTree(nodeType, m_scrollLayerID ? m_scrollLayerID : scrollingCoordinator->uniqueScrollLayerID(), parentID);
}

void RenderLayerBacking::detachFromScrollingCoordinator()
{
    // If m_scrollLayerID is 0, then this backing is not attached to the ScrollingCoordinator.
    if (!m_scrollLayerID)
        return;

    ScrollingCoordinator* scrollingCoordinator = scrollingCoordinatorFromLayer(m_owningLayer);
    if (!scrollingCoordinator)
        return;

    scrollingCoordinator->detachFromStateTree(m_scrollLayerID);
    m_scrollLayerID = 0;
}

GraphicsLayerPaintingPhase RenderLayerBacking::paintingPhaseForPrimaryLayer() const
{
    unsigned phase = 0;
    if (!m_backgroundLayer)
        phase |= GraphicsLayerPaintBackground;
    if (!m_foregroundLayer)
        phase |= GraphicsLayerPaintForeground;
    if (!m_maskLayer)
        phase |= GraphicsLayerPaintMask;

    if (m_scrollingContentsLayer) {
        phase &= ~GraphicsLayerPaintForeground;
        phase |= GraphicsLayerPaintCompositedScroll;
    }

    return static_cast<GraphicsLayerPaintingPhase>(phase);
}

float RenderLayerBacking::compositingOpacity(float rendererOpacity) const
{
    float finalOpacity = rendererOpacity;
    
    for (RenderLayer* curr = m_owningLayer.parent(); curr; curr = curr->parent()) {
        // We only care about parents that are stacking contexts.
        // Recall that opacity creates stacking context.
        if (!curr->isStackingContainer())
            continue;
        
        // If we found a compositing layer, we want to compute opacity
        // relative to it. So we can break here.
        if (curr->isComposited())
            break;
        
        finalOpacity *= curr->renderer().opacity();
    }

    return finalOpacity;
}

static bool hasBoxDecorations(const RenderStyle* style)
{
    return style->hasBorder() || style->hasBorderRadius() || style->hasOutline() || style->hasAppearance() || style->boxShadow() || style->hasFilter();
}

static bool canCreateTiledImage(const RenderStyle*);

static bool hasBoxDecorationsOrBackgroundImage(const RenderStyle* style)
{
    if (hasBoxDecorations(style))
        return true;

    if (!style->hasBackgroundImage())
        return false;

    return !GraphicsLayer::supportsContentsTiling() || !canCreateTiledImage(style);
}

static bool hasPerspectiveOrPreserves3D(const RenderStyle* style)
{
    return style->hasPerspective() || style->preserves3D();
}

Color RenderLayerBacking::rendererBackgroundColor() const
{
    RenderElement* backgroundRenderer = &renderer();
    if (backgroundRenderer->isRoot())
        backgroundRenderer = backgroundRenderer->rendererForRootBackground();

    return backgroundRenderer->style().visitedDependentColor(CSSPropertyBackgroundColor);
}

void RenderLayerBacking::updateDirectlyCompositedBackgroundColor(bool isSimpleContainer, bool& didUpdateContentsRect)
{
    if (!isSimpleContainer) {
        m_graphicsLayer->setContentsToSolidColor(Color());
        return;
    }

    Color backgroundColor = rendererBackgroundColor();

    // An unset (invalid) color will remove the solid color.
    m_graphicsLayer->setContentsToSolidColor(backgroundColor);
    IntRect contentsRect = backgroundBox();
    m_graphicsLayer->setContentsRect(contentsRect);
    m_graphicsLayer->setContentsClippingRect(contentsRect);
    didUpdateContentsRect = true;
}

bool canCreateTiledImage(const RenderStyle* style)
{
    const FillLayer* fillLayer = style->backgroundLayers();
    if (fillLayer->next())
        return false;

    if (!fillLayer->imagesAreLoaded())
        return false;

    if (fillLayer->attachment() != ScrollBackgroundAttachment)
        return false;

    Color color = style->visitedDependentColor(CSSPropertyBackgroundColor);

    // FIXME: Allow color+image compositing when it makes sense.
    // For now bailing out.
    if (color.isValid() && color.alpha())
        return false;

    StyleImage* styleImage = fillLayer->image();

    // FIXME: support gradients with isGeneratedImage.
    if (!styleImage->isCachedImage())
        return false;

    Image* image = styleImage->cachedImage()->image();
    if (!image->isBitmapImage())
        return false;

    return true;
}

void RenderLayerBacking::updateDirectlyCompositedBackgroundImage(bool isSimpleContainer, bool& didUpdateContentsRect)
{
    if (!GraphicsLayer::supportsContentsTiling())
        return;

    if (isDirectlyCompositedImage())
        return;

    const RenderStyle& style = renderer().style();

    if (!isSimpleContainer || !style.hasBackgroundImage()) {
        m_graphicsLayer->setContentsToImage(0);
        return;
    }

    IntRect destRect = backgroundBox();
    IntPoint phase;
    IntSize tileSize;

    RefPtr<Image> image = style.backgroundLayers()->image()->cachedImage()->image();
    toRenderBox(renderer()).getGeometryForBackgroundImage(&m_owningLayer.renderer(), destRect, phase, tileSize);
    m_graphicsLayer->setContentsTileSize(tileSize);
    m_graphicsLayer->setContentsTilePhase(phase);
    m_graphicsLayer->setContentsRect(destRect);
    m_graphicsLayer->setContentsClippingRect(destRect);
    m_graphicsLayer->setContentsToImage(image.get());
    didUpdateContentsRect = true;
}

void RenderLayerBacking::updateRootLayerConfiguration()
{
    if (!m_usingTiledCacheLayer)
        return;

    Color backgroundColor;
    bool viewIsTransparent = compositor().viewHasTransparentBackground(&backgroundColor);

    if (m_backgroundLayerPaintsFixedRootBackground && m_backgroundLayer) {
        m_backgroundLayer->setBackgroundColor(backgroundColor);
        m_backgroundLayer->setContentsOpaque(!viewIsTransparent);

        m_graphicsLayer->setBackgroundColor(Color());
        m_graphicsLayer->setContentsOpaque(false);
    } else {
        m_graphicsLayer->setBackgroundColor(backgroundColor);
        m_graphicsLayer->setContentsOpaque(!viewIsTransparent);
    }
}

static bool supportsDirectBoxDecorationsComposition(const RenderObject& renderer)
{
    if (!GraphicsLayer::supportsBackgroundColorContent())
        return false;

    if (renderer.hasClip())
        return false;

    if (hasBoxDecorationsOrBackgroundImage(&renderer.style()))
        return false;

    // FIXME: We can't create a directly composited background if this
    // layer will have children that intersect with the background layer.
    // A better solution might be to introduce a flattening layer if
    // we do direct box decoration composition.
    // https://bugs.webkit.org/show_bug.cgi?id=119461
    if (hasPerspectiveOrPreserves3D(&renderer.style()))
        return false;

    // FIXME: we should be able to allow backgroundComposite; However since this is not a common use case it has been deferred for now.
    if (renderer.style().backgroundComposite() != CompositeSourceOver)
        return false;

    if (renderer.style().backgroundClip() == TextFillBox)
        return false;

    return true;
}

bool RenderLayerBacking::paintsBoxDecorations() const
{
    if (!m_owningLayer.hasVisibleBoxDecorations())
        return false;

    if (!supportsDirectBoxDecorationsComposition(renderer()))
        return true;

    return false;
}

bool RenderLayerBacking::paintsChildren() const
{
    if (m_owningLayer.hasVisibleContent() && m_owningLayer.hasNonEmptyChildRenderers())
        return true;

    if (hasVisibleNonCompositingDescendantLayers())
        return true;

    return false;
}

static bool isRestartedPlugin(RenderObject* renderer)
{
    if (!renderer->isEmbeddedObject())
        return false;

    Element* element = toElement(renderer->node());
    if (!element || !element->isPluginElement())
        return false;

    return toHTMLPlugInElement(element)->isRestartedPlugin();
}

static bool isCompositedPlugin(RenderObject* renderer)
{
    return renderer->isEmbeddedObject() && toRenderEmbeddedObject(renderer)->allowsAcceleratedCompositing();
}

// A "simple container layer" is a RenderLayer which has no visible content to render.
// It may have no children, or all its children may be themselves composited.
// This is a useful optimization, because it allows us to avoid allocating backing store.
bool RenderLayerBacking::isSimpleContainerCompositingLayer() const
{
    if (renderer().hasMask()) // masks require special treatment
        return false;

    if (renderer().isReplaced() && (!isCompositedPlugin(&renderer()) || isRestartedPlugin(&renderer())))
        return false;

    if (paintsBoxDecorations() || paintsChildren())
        return false;

    if (renderer().isRenderNamedFlowFragmentContainer())
        return false;

    if (renderer().isRenderView()) {
        // Look to see if the root object has a non-simple background
        RenderObject* rootObject = renderer().document().documentElement() ? renderer().document().documentElement()->renderer() : 0;
        if (!rootObject)
            return false;
        
        RenderStyle* style = &rootObject->style();
        
        // Reject anything that has a border, a border-radius or outline,
        // or is not a simple background (no background, or solid color).
        if (hasBoxDecorationsOrBackgroundImage(style))
            return false;
        
        // Now look at the body's renderer.
        HTMLElement* body = renderer().document().body();
        RenderObject* bodyObject = (body && body->hasLocalName(bodyTag)) ? body->renderer() : 0;
        if (!bodyObject)
            return false;
        
        style = &bodyObject->style();
        
        if (hasBoxDecorationsOrBackgroundImage(style))
            return false;
    }

    return true;
}

static bool hasVisibleNonCompositingDescendant(RenderLayer& parent)
{
    // FIXME: We shouldn't be called with a stale z-order lists. See bug 85512.
    parent.updateLayerListsIfNeeded();

#if !ASSERT_DISABLED
    LayerListMutationDetector mutationChecker(&parent);
#endif

    if (Vector<RenderLayer*>* normalFlowList = parent.normalFlowList()) {
        size_t listSize = normalFlowList->size();
        for (size_t i = 0; i < listSize; ++i) {
            RenderLayer* curLayer = normalFlowList->at(i);
            if (!curLayer->isComposited()
                && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(*curLayer)))
                return true;
        }
    }

    if (parent.isStackingContainer()) {
        if (!parent.hasVisibleDescendant())
            return false;

        // Use the m_hasCompositingDescendant bit to optimize?
        if (Vector<RenderLayer*>* negZOrderList = parent.negZOrderList()) {
            size_t listSize = negZOrderList->size();
            for (size_t i = 0; i < listSize; ++i) {
                RenderLayer* curLayer = negZOrderList->at(i);
                if (!curLayer->isComposited()
                    && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(*curLayer)))
                    return true;
            }
        }

        if (Vector<RenderLayer*>* posZOrderList = parent.posZOrderList()) {
            size_t listSize = posZOrderList->size();
            for (size_t i = 0; i < listSize; ++i) {
                RenderLayer* curLayer = posZOrderList->at(i);
                if (!curLayer->isComposited()
                    && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(*curLayer)))
                    return true;
            }
        }
    }

    return false;
}

// Conservative test for having no rendered children.
bool RenderLayerBacking::hasVisibleNonCompositingDescendantLayers() const
{
    return hasVisibleNonCompositingDescendant(m_owningLayer);
}

bool RenderLayerBacking::containsPaintedContent(bool isSimpleContainer) const
{
    if (isSimpleContainer || paintsIntoWindow() || paintsIntoCompositedAncestor() || m_artificiallyInflatedBounds || m_owningLayer.isReflection())
        return false;

    if (isDirectlyCompositedImage())
        return false;

    // FIXME: we could optimize cases where the image, video or canvas is known to fill the border box entirely,
    // and set background color on the layer in that case, instead of allocating backing store and painting.
#if ENABLE(VIDEO)
    if (renderer().isVideo() && toRenderVideo(renderer()).shouldDisplayVideo())
        return m_owningLayer.hasBoxDecorationsOrBackground();
#endif
#if PLATFORM(MAC) && USE(CA)
#elif ENABLE(WEBGL) || ENABLE(ACCELERATED_2D_CANVAS)
    if (isAcceleratedCanvas(&renderer()))
        return m_owningLayer.hasBoxDecorationsOrBackground();
#endif

    return true;
}

// An image can be directly compositing if it's the sole content of the layer, and has no box decorations
// that require painting. Direct compositing saves backing store.
bool RenderLayerBacking::isDirectlyCompositedImage() const
{
    if (!renderer().isImage() || m_owningLayer.hasBoxDecorationsOrBackground() || renderer().hasClip())
        return false;

    RenderImage& imageRenderer = toRenderImage(renderer());
    if (CachedImage* cachedImage = imageRenderer.cachedImage()) {
        if (!cachedImage->hasImage())
            return false;

        Image* image = cachedImage->imageForRenderer(&imageRenderer);
        if (!image->isBitmapImage())
            return false;

        if (image->orientationForCurrentFrame() != DefaultImageOrientation)
            return false;

        return m_graphicsLayer->shouldDirectlyCompositeImage(image);
    }

    return false;
}

void RenderLayerBacking::contentChanged(ContentChangeType changeType)
{
    if ((changeType == ImageChanged) && isDirectlyCompositedImage()) {
        updateImageContents();
        return;
    }

    if ((changeType == BackgroundImageChanged) && canCreateTiledImage(&renderer().style()))
        updateGraphicsLayerGeometry();

    if ((changeType == MaskImageChanged) && m_maskLayer) {
        // The composited layer bounds relies on box->maskClipRect(), which changes
        // when the mask image becomes available.
        updateAfterLayout(CompositingChildrenOnly | IsUpdateRoot);
    }

#if ENABLE(WEBGL) || ENABLE(ACCELERATED_2D_CANVAS)
    if ((changeType == CanvasChanged || changeType == CanvasPixelsChanged) && isAcceleratedCanvas(&renderer())) {
        m_graphicsLayer->setContentsNeedsDisplay();
        return;
    }
#endif
}

void RenderLayerBacking::updateImageContents()
{
    ASSERT(renderer().isImage());
    RenderImage& imageRenderer = toRenderImage(renderer());

    CachedImage* cachedImage = imageRenderer.cachedImage();
    if (!cachedImage)
        return;

    Image* image = cachedImage->imageForRenderer(&imageRenderer);
    if (!image)
        return;

    // We have to wait until the image is fully loaded before setting it on the layer.
    if (!cachedImage->isLoaded())
        return;

    // This is a no-op if the layer doesn't have an inner layer for the image.
    m_graphicsLayer->setContentsRect(pixelSnappedIntRect(contentsBox()));

    LayoutRect contentsClippingRect = imageRenderer.contentBoxRect();
    contentsClippingRect.move(contentOffsetInCompostingLayer());
    m_graphicsLayer->setContentsClippingRect(pixelSnappedIntRect(contentsClippingRect));

    m_graphicsLayer->setContentsToImage(image);
    bool isSimpleContainer = false;
    updateDrawsContent(isSimpleContainer);
    
    // Image animation is "lazy", in that it automatically stops unless someone is drawing
    // the image. So we have to kick the animation each time; this has the downside that the
    // image will keep animating, even if its layer is not visible.
    image->startAnimation();
}

FloatPoint3D RenderLayerBacking::computeTransformOrigin(const IntRect& borderBox) const
{
    const RenderStyle& style = renderer().style();

    FloatPoint3D origin;
    origin.setX(floatValueForLength(style.transformOriginX(), borderBox.width()));
    origin.setY(floatValueForLength(style.transformOriginY(), borderBox.height()));
    origin.setZ(style.transformOriginZ());

    return origin;
}

FloatPoint RenderLayerBacking::computePerspectiveOrigin(const IntRect& borderBox) const
{
    const RenderStyle& style = renderer().style();

    float boxWidth = borderBox.width();
    float boxHeight = borderBox.height();

    FloatPoint origin;
    origin.setX(floatValueForLength(style.perspectiveOriginX(), boxWidth));
    origin.setY(floatValueForLength(style.perspectiveOriginY(), boxHeight));

    return origin;
}

// Return the offset from the top-left of this compositing layer at which the renderer's contents are painted.
LayoutSize RenderLayerBacking::contentOffsetInCompostingLayer() const
{
    return LayoutSize(-m_compositedBounds.x(), -m_compositedBounds.y());
}

LayoutRect RenderLayerBacking::contentsBox() const
{
    if (!renderer().isBox())
        return LayoutRect();

    RenderBox& renderBox = toRenderBox(renderer());
    LayoutRect contentsRect;
#if ENABLE(VIDEO)
    if (renderBox.isVideo())
        contentsRect = toRenderVideo(renderBox).videoBox();
    else
#endif
    if (renderBox.isRenderReplaced()) {
        RenderReplaced& renderReplaced = *toRenderReplaced(&renderBox);
        contentsRect = renderReplaced.replacedContentRect(renderBox.intrinsicSize());
    } else
        contentsRect = renderBox.contentBoxRect();

    contentsRect.move(contentOffsetInCompostingLayer());
    return contentsRect;
}

static LayoutRect backgroundRectForBox(const RenderBox& box)
{
    switch (box.style().backgroundClip()) {
    case BorderFillBox:
        return box.borderBoxRect();
    case PaddingFillBox:
        return box.paddingBoxRect();
    case ContentFillBox:
        return box.contentBoxRect();
    case TextFillBox:
        break;
    }

    ASSERT_NOT_REACHED();
    return LayoutRect();
}

IntRect RenderLayerBacking::backgroundBox() const
{
    if (!renderer().isBox())
        return IntRect();

    LayoutRect backgroundBox = backgroundRectForBox(toRenderBox(renderer()));
    backgroundBox.move(contentOffsetInCompostingLayer());
    return pixelSnappedIntRect(backgroundBox);
}

GraphicsLayer* RenderLayerBacking::parentForSublayers() const
{
    if (m_scrollingContentsLayer)
        return m_scrollingContentsLayer.get();

    return m_childContainmentLayer ? m_childContainmentLayer.get() : m_graphicsLayer.get();
}

GraphicsLayer* RenderLayerBacking::childForSuperlayers() const
{
    if (m_ancestorClippingLayer)
        return m_ancestorClippingLayer.get();

    if (m_contentsContainmentLayer)
        return m_contentsContainmentLayer.get();
    
    return m_graphicsLayer.get();
}

bool RenderLayerBacking::paintsIntoWindow() const
{
    if (m_usingTiledCacheLayer)
        return false;

    if (m_owningLayer.isRootLayer()) {
#if PLATFORM(BLACKBERRY) || USE(COORDINATED_GRAPHICS)
        if (compositor().inForcedCompositingMode())
            return false;
#endif

        return compositor().rootLayerAttachment() != RenderLayerCompositor::RootLayerAttachedViaEnclosingFrame;
    }
    
    return false;
}

void RenderLayerBacking::setRequiresOwnBackingStore(bool requiresOwnBacking)
{
    if (requiresOwnBacking == m_requiresOwnBackingStore)
        return;
    
    m_requiresOwnBackingStore = requiresOwnBacking;

    // This affects the answer to paintsIntoCompositedAncestor(), which in turn affects
    // cached clip rects, so when it changes we have to clear clip rects on descendants.
    m_owningLayer.clearClipRectsIncludingDescendants(PaintingClipRects);
    m_owningLayer.computeRepaintRectsIncludingDescendants();
    
    compositor().repaintInCompositedAncestor(m_owningLayer, compositedBounds());
}

#if ENABLE(CSS_COMPOSITING)
void RenderLayerBacking::setBlendMode(BlendMode)
{
}
#endif

void RenderLayerBacking::setContentsNeedDisplay()
{
    ASSERT(!paintsIntoCompositedAncestor());

    FrameView& frameView = owningLayer().renderer().view().frameView();
    if (m_isMainFrameRenderViewLayer && frameView.isTrackingRepaints())
        frameView.addTrackedRepaintRect(owningLayer().absoluteBoundingBox());
    
    if (m_graphicsLayer && m_graphicsLayer->drawsContent())
        m_graphicsLayer->setNeedsDisplay();
    
    if (m_foregroundLayer && m_foregroundLayer->drawsContent())
        m_foregroundLayer->setNeedsDisplay();

    if (m_backgroundLayer && m_backgroundLayer->drawsContent())
        m_backgroundLayer->setNeedsDisplay();

    if (m_maskLayer && m_maskLayer->drawsContent())
        m_maskLayer->setNeedsDisplay();

    if (m_scrollingContentsLayer && m_scrollingContentsLayer->drawsContent())
        m_scrollingContentsLayer->setNeedsDisplay();
}

// r is in the coordinate space of the layer's render object
void RenderLayerBacking::setContentsNeedDisplayInRect(const IntRect& r)
{
    ASSERT(!paintsIntoCompositedAncestor());

    FrameView& frameView = owningLayer().renderer().view().frameView();
    if (m_isMainFrameRenderViewLayer && frameView.isTrackingRepaints())
        frameView.addTrackedRepaintRect(pixelSnappedIntRect(r));

    if (m_graphicsLayer && m_graphicsLayer->drawsContent()) {
        IntRect layerDirtyRect = r;
        layerDirtyRect.move(-m_graphicsLayer->offsetFromRenderer());
        m_graphicsLayer->setNeedsDisplayInRect(layerDirtyRect);
    }

    if (m_foregroundLayer && m_foregroundLayer->drawsContent()) {
        IntRect layerDirtyRect = r;
        layerDirtyRect.move(-m_foregroundLayer->offsetFromRenderer());
        m_foregroundLayer->setNeedsDisplayInRect(layerDirtyRect);
    }

    // FIXME: need to split out repaints for the background.
    if (m_backgroundLayer && m_backgroundLayer->drawsContent()) {
        IntRect layerDirtyRect = r;
        layerDirtyRect.move(-m_backgroundLayer->offsetFromRenderer());
        m_backgroundLayer->setNeedsDisplayInRect(layerDirtyRect);
    }

    if (m_maskLayer && m_maskLayer->drawsContent()) {
        IntRect layerDirtyRect = r;
        layerDirtyRect.move(-m_maskLayer->offsetFromRenderer());
        m_maskLayer->setNeedsDisplayInRect(layerDirtyRect);
    }

    if (m_scrollingContentsLayer && m_scrollingContentsLayer->drawsContent()) {
        IntRect layerDirtyRect = r;
        layerDirtyRect.move(-m_scrollingContentsLayer->offsetFromRenderer());
        m_scrollingContentsLayer->setNeedsDisplayInRect(layerDirtyRect);
    }
}

void RenderLayerBacking::paintIntoLayer(const GraphicsLayer* graphicsLayer, GraphicsContext* context,
                    const IntRect& paintDirtyRect, // In the coords of rootLayer.
                    PaintBehavior paintBehavior, GraphicsLayerPaintingPhase paintingPhase)
{
    if (paintsIntoWindow() || paintsIntoCompositedAncestor()) {
        ASSERT_NOT_REACHED();
        return;
    }

    FontCachePurgePreventer fontCachePurgePreventer;
    
    RenderLayer::PaintLayerFlags paintFlags = 0;
    if (paintingPhase & GraphicsLayerPaintBackground)
        paintFlags |= RenderLayer::PaintLayerPaintingCompositingBackgroundPhase;
    if (paintingPhase & GraphicsLayerPaintForeground)
        paintFlags |= RenderLayer::PaintLayerPaintingCompositingForegroundPhase;
    if (paintingPhase & GraphicsLayerPaintMask)
        paintFlags |= RenderLayer::PaintLayerPaintingCompositingMaskPhase;
    if (paintingPhase & GraphicsLayerPaintOverflowContents)
        paintFlags |= RenderLayer::PaintLayerPaintingOverflowContents;
    if (paintingPhase & GraphicsLayerPaintCompositedScroll)
        paintFlags |= RenderLayer::PaintLayerPaintingCompositingScrollingPhase;

    if (graphicsLayer == m_backgroundLayer.get())
        paintFlags |= (RenderLayer::PaintLayerPaintingRootBackgroundOnly | RenderLayer::PaintLayerPaintingCompositingForegroundPhase); // Need PaintLayerPaintingCompositingForegroundPhase to walk child layers.
    else if (compositor().fixedRootBackgroundLayer())
        paintFlags |= RenderLayer::PaintLayerPaintingSkipRootBackground;
    
    // FIXME: GraphicsLayers need a way to split for RenderRegions.
    RenderLayer::LayerPaintingInfo paintingInfo(&m_owningLayer, paintDirtyRect, paintBehavior, m_subpixelAccumulation);
    m_owningLayer.paintLayerContents(context, paintingInfo, paintFlags);

    if (m_owningLayer.containsDirtyOverlayScrollbars())
        m_owningLayer.paintLayerContents(context, paintingInfo, paintFlags | RenderLayer::PaintLayerPaintingOverlayScrollbars);

    compositor().didPaintBacking(this);

    ASSERT(!m_owningLayer.m_usedTransparency);
}

static void paintScrollbar(Scrollbar* scrollbar, GraphicsContext& context, const IntRect& clip)
{
    if (!scrollbar)
        return;

    context.save();
    const IntRect& scrollbarRect = scrollbar->frameRect();
    context.translate(-scrollbarRect.x(), -scrollbarRect.y());
    IntRect transformedClip = clip;
    transformedClip.moveBy(scrollbarRect.location());
    scrollbar->paint(&context, transformedClip);
    context.restore();
}

// Up-call from compositing layer drawing callback.
void RenderLayerBacking::paintContents(const GraphicsLayer* graphicsLayer, GraphicsContext& context, GraphicsLayerPaintingPhase paintingPhase, const IntRect& clip)
{
#ifndef NDEBUG
    if (Page* page = renderer().frame().page())
        page->setIsPainting(true);
#endif

    if (graphicsLayer == m_graphicsLayer.get()
        || graphicsLayer == m_foregroundLayer.get()
        || graphicsLayer == m_backgroundLayer.get()
        || graphicsLayer == m_maskLayer.get()
        || graphicsLayer == m_scrollingContentsLayer.get()) {
        InspectorInstrumentation::willPaint(&renderer());

        // The dirtyRect is in the coords of the painting root.
        IntRect dirtyRect = clip;
        if (!(paintingPhase & GraphicsLayerPaintOverflowContents))
            dirtyRect.intersect(enclosingIntRect(compositedBounds()));

        // We have to use the same root as for hit testing, because both methods can compute and cache clipRects.
        paintIntoLayer(graphicsLayer, &context, dirtyRect, PaintBehaviorNormal, paintingPhase);

        InspectorInstrumentation::didPaint(&renderer(), &context, clip);
    } else if (graphicsLayer == layerForHorizontalScrollbar()) {
        paintScrollbar(m_owningLayer.horizontalScrollbar(), context, clip);
    } else if (graphicsLayer == layerForVerticalScrollbar()) {
        paintScrollbar(m_owningLayer.verticalScrollbar(), context, clip);
    } else if (graphicsLayer == layerForScrollCorner()) {
        const IntRect& scrollCornerAndResizer = m_owningLayer.scrollCornerAndResizerRect();
        context.save();
        context.translate(-scrollCornerAndResizer.x(), -scrollCornerAndResizer.y());
        IntRect transformedClip = clip;
        transformedClip.moveBy(scrollCornerAndResizer.location());
        m_owningLayer.paintScrollCorner(&context, IntPoint(), transformedClip);
        m_owningLayer.paintResizer(&context, IntPoint(), transformedClip);
        context.restore();
    }
#ifndef NDEBUG
    if (Page* page = renderer().frame().page())
        page->setIsPainting(false);
#endif
}

float RenderLayerBacking::pageScaleFactor() const
{
    return compositor().pageScaleFactor();
}

float RenderLayerBacking::deviceScaleFactor() const
{
    return compositor().deviceScaleFactor();
}

void RenderLayerBacking::didCommitChangesForLayer(const GraphicsLayer* layer) const
{
    compositor().didFlushChangesForLayer(m_owningLayer, layer);
}

bool RenderLayerBacking::getCurrentTransform(const GraphicsLayer* graphicsLayer, TransformationMatrix& transform) const
{
    GraphicsLayer* transformedLayer = m_contentsContainmentLayer.get() ? m_contentsContainmentLayer.get() : m_graphicsLayer.get();
    if (graphicsLayer != transformedLayer)
        return false;

    if (m_owningLayer.hasTransform()) {
        transform = m_owningLayer.currentTransform(RenderStyle::ExcludeTransformOrigin);
        return true;
    }
    return false;
}

bool RenderLayerBacking::isTrackingRepaints() const
{
    return static_cast<GraphicsLayerClient&>(compositor()).isTrackingRepaints();
}

bool RenderLayerBacking::shouldSkipLayerInDump(const GraphicsLayer* layer) const
{
    // Skip the root tile cache's flattening layer.
    return m_isMainFrameRenderViewLayer && layer && layer == m_childContainmentLayer.get();
}

bool RenderLayerBacking::shouldDumpPropertyForLayer(const GraphicsLayer* layer, const char* propertyName) const
{
    // For backwards compatibility with WebKit1 and other platforms,
    // skip some properties on the root tile cache.
    if (m_isMainFrameRenderViewLayer && layer == m_graphicsLayer.get()) {
        if (!strcmp(propertyName, "drawsContent"))
            return false;

        // Background color could be of interest to tests or other dumpers if it's non-white.
        if (!strcmp(propertyName, "backgroundColor") && layer->backgroundColor() == Color::white)
            return false;

        // The root tile cache's repaints will show up at the top with FrameView's,
        // so don't dump them twice.
        if (!strcmp(propertyName, "repaintRects"))
            return false;
    }

    return true;
}

#ifndef NDEBUG
void RenderLayerBacking::verifyNotPainting()
{
    ASSERT(!renderer().frame().page() || !renderer().frame().page()->isPainting());
}
#endif

bool RenderLayerBacking::startAnimation(double timeOffset, const Animation* anim, const KeyframeList& keyframes)
{
    bool hasOpacity = keyframes.containsProperty(CSSPropertyOpacity);
    bool hasTransform = renderer().isBox() && keyframes.containsProperty(CSSPropertyWebkitTransform);
#if ENABLE(CSS_FILTERS)
    bool hasFilter = keyframes.containsProperty(CSSPropertyWebkitFilter);
#else
    bool hasFilter = false;
#endif

    if (!hasOpacity && !hasTransform && !hasFilter)
        return false;
    
    KeyframeValueList transformVector(AnimatedPropertyWebkitTransform);
    KeyframeValueList opacityVector(AnimatedPropertyOpacity);
#if ENABLE(CSS_FILTERS)
    KeyframeValueList filterVector(AnimatedPropertyWebkitFilter);
#endif

    size_t numKeyframes = keyframes.size();
    for (size_t i = 0; i < numKeyframes; ++i) {
        const KeyframeValue& currentKeyframe = keyframes[i];
        const RenderStyle* keyframeStyle = currentKeyframe.style();
        double key = currentKeyframe.key();

        if (!keyframeStyle)
            continue;
            
        // Get timing function.
        RefPtr<TimingFunction> tf = keyframeStyle->hasAnimations() ? (*keyframeStyle->animations()).animation(0).timingFunction() : 0;
        
        bool isFirstOrLastKeyframe = key == 0 || key == 1;
        if ((hasTransform && isFirstOrLastKeyframe) || currentKeyframe.containsProperty(CSSPropertyWebkitTransform))
            transformVector.insert(TransformAnimationValue::create(key, keyframeStyle->transform(), tf));

        if ((hasOpacity && isFirstOrLastKeyframe) || currentKeyframe.containsProperty(CSSPropertyOpacity))
            opacityVector.insert(FloatAnimationValue::create(key, keyframeStyle->opacity(), tf));

#if ENABLE(CSS_FILTERS)
        if ((hasFilter && isFirstOrLastKeyframe) || currentKeyframe.containsProperty(CSSPropertyWebkitFilter))
            filterVector.insert(FilterAnimationValue::create(key, keyframeStyle->filter(), tf));
#endif
    }

    if (renderer().frame().page() && !renderer().frame().page()->settings().acceleratedCompositedAnimationsEnabled())
        return false;

    bool didAnimate = false;

    if (hasTransform && m_graphicsLayer->addAnimation(transformVector, toRenderBox(renderer()).pixelSnappedBorderBoxRect().size(), anim, keyframes.animationName(), timeOffset))
        didAnimate = true;

    if (hasOpacity && m_graphicsLayer->addAnimation(opacityVector, IntSize(), anim, keyframes.animationName(), timeOffset))
        didAnimate = true;

#if ENABLE(CSS_FILTERS)
    if (hasFilter && m_graphicsLayer->addAnimation(filterVector, IntSize(), anim, keyframes.animationName(), timeOffset))
        didAnimate = true;
#endif

    return didAnimate;
}

void RenderLayerBacking::animationPaused(double timeOffset, const String& animationName)
{
    m_graphicsLayer->pauseAnimation(animationName, timeOffset);
}

void RenderLayerBacking::animationFinished(const String& animationName)
{
    m_graphicsLayer->removeAnimation(animationName);
}

bool RenderLayerBacking::startTransition(double timeOffset, CSSPropertyID property, const RenderStyle* fromStyle, const RenderStyle* toStyle)
{
    bool didAnimate = false;

    ASSERT(property != CSSPropertyInvalid);

    if (property == CSSPropertyOpacity) {
        const Animation* opacityAnim = toStyle->transitionForProperty(CSSPropertyOpacity);
        if (opacityAnim && !opacityAnim->isEmptyOrZeroDuration()) {
            KeyframeValueList opacityVector(AnimatedPropertyOpacity);
            opacityVector.insert(FloatAnimationValue::create(0, compositingOpacity(fromStyle->opacity())));
            opacityVector.insert(FloatAnimationValue::create(1, compositingOpacity(toStyle->opacity())));
            // The boxSize param is only used for transform animations (which can only run on RenderBoxes), so we pass an empty size here.
            if (m_graphicsLayer->addAnimation(opacityVector, IntSize(), opacityAnim, GraphicsLayer::animationNameForTransition(AnimatedPropertyOpacity), timeOffset)) {
                // To ensure that the correct opacity is visible when the animation ends, also set the final opacity.
                updateOpacity(toStyle);
                didAnimate = true;
            }
        }
    }

    if (property == CSSPropertyWebkitTransform && m_owningLayer.hasTransform()) {
        const Animation* transformAnim = toStyle->transitionForProperty(CSSPropertyWebkitTransform);
        if (transformAnim && !transformAnim->isEmptyOrZeroDuration()) {
            KeyframeValueList transformVector(AnimatedPropertyWebkitTransform);
            transformVector.insert(TransformAnimationValue::create(0, fromStyle->transform()));
            transformVector.insert(TransformAnimationValue::create(1, toStyle->transform()));
            if (m_graphicsLayer->addAnimation(transformVector, toRenderBox(renderer()).pixelSnappedBorderBoxRect().size(), transformAnim, GraphicsLayer::animationNameForTransition(AnimatedPropertyWebkitTransform), timeOffset)) {
                // To ensure that the correct transform is visible when the animation ends, also set the final transform.
                updateTransform(toStyle);
                didAnimate = true;
            }
        }
    }

#if ENABLE(CSS_FILTERS)
    if (property == CSSPropertyWebkitFilter && m_owningLayer.hasFilter()) {
        const Animation* filterAnim = toStyle->transitionForProperty(CSSPropertyWebkitFilter);
        if (filterAnim && !filterAnim->isEmptyOrZeroDuration()) {
            KeyframeValueList filterVector(AnimatedPropertyWebkitFilter);
            filterVector.insert(FilterAnimationValue::create(0, fromStyle->filter()));
            filterVector.insert(FilterAnimationValue::create(1, toStyle->filter()));
            if (m_graphicsLayer->addAnimation(filterVector, IntSize(), filterAnim, GraphicsLayer::animationNameForTransition(AnimatedPropertyWebkitFilter), timeOffset)) {
                // To ensure that the correct filter is visible when the animation ends, also set the final filter.
                updateFilters(toStyle);
                didAnimate = true;
            }
        }
    }
#endif

    return didAnimate;
}

void RenderLayerBacking::transitionPaused(double timeOffset, CSSPropertyID property)
{
    AnimatedPropertyID animatedProperty = cssToGraphicsLayerProperty(property);
    if (animatedProperty != AnimatedPropertyInvalid)
        m_graphicsLayer->pauseAnimation(GraphicsLayer::animationNameForTransition(animatedProperty), timeOffset);
}

void RenderLayerBacking::transitionFinished(CSSPropertyID property)
{
    AnimatedPropertyID animatedProperty = cssToGraphicsLayerProperty(property);
    if (animatedProperty != AnimatedPropertyInvalid)
        m_graphicsLayer->removeAnimation(GraphicsLayer::animationNameForTransition(animatedProperty));
}

void RenderLayerBacking::notifyAnimationStarted(const GraphicsLayer*, double time)
{
    renderer().animation().notifyAnimationStarted(&renderer(), time);
}

void RenderLayerBacking::notifyFlushRequired(const GraphicsLayer* layer)
{
    if (renderer().documentBeingDestroyed())
        return;
    compositor().scheduleLayerFlush(layer->canThrottleLayerFlush());
}

void RenderLayerBacking::notifyFlushBeforeDisplayRefresh(const GraphicsLayer* layer)
{
    compositor().notifyFlushBeforeDisplayRefresh(layer);
}

// This is used for the 'freeze' API, for testing only.
void RenderLayerBacking::suspendAnimations(double time)
{
    m_graphicsLayer->suspendAnimations(time);
}

void RenderLayerBacking::resumeAnimations()
{
    m_graphicsLayer->resumeAnimations();
}

LayoutRect RenderLayerBacking::compositedBounds() const
{
    return m_compositedBounds;
}

void RenderLayerBacking::setCompositedBounds(const LayoutRect& bounds)
{
    m_compositedBounds = bounds;
}

CSSPropertyID RenderLayerBacking::graphicsLayerToCSSProperty(AnimatedPropertyID property)
{
    CSSPropertyID cssProperty = CSSPropertyInvalid;
    switch (property) {
        case AnimatedPropertyWebkitTransform:
            cssProperty = CSSPropertyWebkitTransform;
            break;
        case AnimatedPropertyOpacity:
            cssProperty = CSSPropertyOpacity;
            break;
        case AnimatedPropertyBackgroundColor:
            cssProperty = CSSPropertyBackgroundColor;
            break;
        case AnimatedPropertyWebkitFilter:
#if ENABLE(CSS_FILTERS)
            cssProperty = CSSPropertyWebkitFilter;
#else
            ASSERT_NOT_REACHED();
#endif
            break;
        case AnimatedPropertyInvalid:
            ASSERT_NOT_REACHED();
    }
    return cssProperty;
}

AnimatedPropertyID RenderLayerBacking::cssToGraphicsLayerProperty(CSSPropertyID cssProperty)
{
    switch (cssProperty) {
        case CSSPropertyWebkitTransform:
            return AnimatedPropertyWebkitTransform;
        case CSSPropertyOpacity:
            return AnimatedPropertyOpacity;
        case CSSPropertyBackgroundColor:
            return AnimatedPropertyBackgroundColor;
#if ENABLE(CSS_FILTERS)
        case CSSPropertyWebkitFilter:
            return AnimatedPropertyWebkitFilter;
#endif
        default:
            // It's fine if we see other css properties here; they are just not accelerated.
            break;
    }
    return AnimatedPropertyInvalid;
}

CompositingLayerType RenderLayerBacking::compositingLayerType() const
{
    if (m_graphicsLayer->hasContentsLayer())
        return MediaCompositingLayer;

    if (m_graphicsLayer->drawsContent())
        return m_graphicsLayer->usingTiledBacking() ? TiledCompositingLayer : NormalCompositingLayer;
    
    return ContainerCompositingLayer;
}

double RenderLayerBacking::backingStoreMemoryEstimate() const
{
    double backingMemory;
    
    // m_ancestorClippingLayer, m_contentsContainmentLayer and m_childContainmentLayer are just used for masking or containment, so have no backing.
    backingMemory = m_graphicsLayer->backingStoreMemoryEstimate();
    if (m_foregroundLayer)
        backingMemory += m_foregroundLayer->backingStoreMemoryEstimate();
    if (m_backgroundLayer)
        backingMemory += m_backgroundLayer->backingStoreMemoryEstimate();
    if (m_maskLayer)
        backingMemory += m_maskLayer->backingStoreMemoryEstimate();

    if (m_scrollingContentsLayer)
        backingMemory += m_scrollingContentsLayer->backingStoreMemoryEstimate();

    if (m_layerForHorizontalScrollbar)
        backingMemory += m_layerForHorizontalScrollbar->backingStoreMemoryEstimate();

    if (m_layerForVerticalScrollbar)
        backingMemory += m_layerForVerticalScrollbar->backingStoreMemoryEstimate();

    if (m_layerForScrollCorner)
        backingMemory += m_layerForScrollCorner->backingStoreMemoryEstimate();
    
    return backingMemory;
}

} // namespace WebCore

#endif // USE(ACCELERATED_COMPOSITING)