diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index b50a0e4..2854bf6 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,5 +1,55 @@
 2019-11-19  Antti Koivisto  <antti@apple.com>
 
+        Move RuleData to a file of its own
+        https://bugs.webkit.org/show_bug.cgi?id=204351
+
+        Reviewed by Anders Carlsson.
+    
+        * Sources.txt:
+        * WebCore.xcodeproj/project.pbxproj:
+        * style/RuleData.cpp: Added.
+        (WebCore::Style::computeMatchBasedOnRuleHash):
+        (WebCore::Style::selectorCanMatchPseudoElement):
+        (WebCore::Style::isCommonAttributeSelectorAttribute):
+        (WebCore::Style::computeContainsUncommonAttributeSelector):
+        (WebCore::Style::determinePropertyWhitelistType):
+        (WebCore::Style::RuleData::RuleData):
+        * style/RuleData.h: Added.
+        (WebCore::Style::RuleData::position const):
+        (WebCore::Style::RuleData::rule const):
+        (WebCore::Style::RuleData::selector const):
+        (WebCore::Style::RuleData::selectorIndex const):
+        (WebCore::Style::RuleData::selectorListIndex const):
+        (WebCore::Style::RuleData::canMatchPseudoElement const):
+        (WebCore::Style::RuleData::matchBasedOnRuleHash const):
+        (WebCore::Style::RuleData::containsUncommonAttributeSelector const):
+        (WebCore::Style::RuleData::linkMatchType const):
+        (WebCore::Style::RuleData::propertyWhitelistType const):
+        (WebCore::Style::RuleData::descendantSelectorIdentifierHashes const):
+        (WebCore::Style::RuleData::disableSelectorFiltering):
+        * style/RuleSet.cpp:
+        (WebCore::Style::computeMatchBasedOnRuleHash): Deleted.
+        (WebCore::Style::selectorCanMatchPseudoElement): Deleted.
+        (WebCore::Style::isCommonAttributeSelectorAttribute): Deleted.
+        (WebCore::Style::computeContainsUncommonAttributeSelector): Deleted.
+        (WebCore::Style::determinePropertyWhitelistType): Deleted.
+        (WebCore::Style::RuleData::RuleData): Deleted.
+        * style/RuleSet.h:
+        (WebCore::Style::RuleData::position const): Deleted.
+        (WebCore::Style::RuleData::rule const): Deleted.
+        (WebCore::Style::RuleData::selector const): Deleted.
+        (WebCore::Style::RuleData::selectorIndex const): Deleted.
+        (WebCore::Style::RuleData::selectorListIndex const): Deleted.
+        (WebCore::Style::RuleData::canMatchPseudoElement const): Deleted.
+        (WebCore::Style::RuleData::matchBasedOnRuleHash const): Deleted.
+        (WebCore::Style::RuleData::containsUncommonAttributeSelector const): Deleted.
+        (WebCore::Style::RuleData::linkMatchType const): Deleted.
+        (WebCore::Style::RuleData::propertyWhitelistType const): Deleted.
+        (WebCore::Style::RuleData::descendantSelectorIdentifierHashes const): Deleted.
+        (WebCore::Style::RuleData::disableSelectorFiltering): Deleted.
+
+2019-11-19  Antti Koivisto  <antti@apple.com>
+
         Move ElementRuleCollector to Style namespace
         https://bugs.webkit.org/show_bug.cgi?id=204329
 
diff --git a/Source/WebCore/Sources.txt b/Source/WebCore/Sources.txt
index ee97339..0c9fdb9 100644
--- a/Source/WebCore/Sources.txt
+++ b/Source/WebCore/Sources.txt
@@ -2344,6 +2344,7 @@
 style/MatchedDeclarationsCache.cpp
 style/PageRuleCollector.cpp
 style/PropertyCascade.cpp
+style/RuleData.cpp
 style/RuleFeature.cpp
 style/RuleSet.cpp
 style/StyleAdjuster.cpp
diff --git a/Source/WebCore/WebCore.xcodeproj/project.pbxproj b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
index 02856dbb..cd13e9f 100644
--- a/Source/WebCore/WebCore.xcodeproj/project.pbxproj
+++ b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
@@ -4841,6 +4841,7 @@
 		E47E276516036ED200EE2AFB /* ExtensionStyleSheets.h in Headers */ = {isa = PBXBuildFile; fileRef = E47E276416036ED200EE2AFB /* ExtensionStyleSheets.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E48137B91DB3B526005C59BF /* StyleValidity.h in Headers */ = {isa = PBXBuildFile; fileRef = E48137B81DB3B526005C59BF /* StyleValidity.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E484A33E23055325009ADE6A /* LineLayoutTraversal.h in Headers */ = {isa = PBXBuildFile; fileRef = E484A33B23055303009ADE6A /* LineLayoutTraversal.h */; settings = {ATTRIBUTES = (Private, ); }; };
+		E4863CFE23842E9E00972158 /* RuleData.h in Headers */ = {isa = PBXBuildFile; fileRef = E4863CFD23842E9E00972158 /* RuleData.h */; };
 		E48944A3180B57D800F165D8 /* SimpleLineLayout.h in Headers */ = {isa = PBXBuildFile; fileRef = E48944A1180B57D800F165D8 /* SimpleLineLayout.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E4916FF7195DF6A0005AB349 /* LayerFlushThrottleState.h in Headers */ = {isa = PBXBuildFile; fileRef = E4916FF6195DF6A0005AB349 /* LayerFlushThrottleState.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		E4946EAF156E64DD00D3297F /* StyleRuleImport.h in Headers */ = {isa = PBXBuildFile; fileRef = E4946EAD156E64DD00D3297F /* StyleRuleImport.h */; settings = {ATTRIBUTES = (Private, ); }; };
@@ -15187,6 +15188,8 @@
 		E48137B81DB3B526005C59BF /* StyleValidity.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = StyleValidity.h; sourceTree = "<group>"; };
 		E484A33B23055303009ADE6A /* LineLayoutTraversal.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = LineLayoutTraversal.h; sourceTree = "<group>"; };
 		E484A33D23055303009ADE6A /* LineLayoutTraversal.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = LineLayoutTraversal.cpp; sourceTree = "<group>"; };
+		E4863CFA23842E8700972158 /* RuleData.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = RuleData.cpp; sourceTree = "<group>"; };
+		E4863CFD23842E9E00972158 /* RuleData.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = RuleData.h; sourceTree = "<group>"; };
 		E48944A0180B57D800F165D8 /* SimpleLineLayout.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = SimpleLineLayout.cpp; sourceTree = "<group>"; };
 		E48944A1180B57D800F165D8 /* SimpleLineLayout.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = SimpleLineLayout.h; sourceTree = "<group>"; };
 		E4916FF6195DF6A0005AB349 /* LayerFlushThrottleState.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = LayerFlushThrottleState.h; sourceTree = "<group>"; };
@@ -27031,6 +27034,8 @@
 				FBDB61A016D6037E00BB3394 /* PageRuleCollector.h */,
 				E4ABABE52361A34200FA4345 /* PropertyCascade.cpp */,
 				E4ABABE22361A32900FA4345 /* PropertyCascade.h */,
+				E4863CFA23842E8700972158 /* RuleData.cpp */,
+				E4863CFD23842E9E00972158 /* RuleData.h */,
 				A79BAD9D161E7F3F00C2E652 /* RuleFeature.cpp */,
 				A79BAD9E161E7F3F00C2E652 /* RuleFeature.h */,
 				A79BAD9F161E7F3F00C2E652 /* RuleSet.cpp */,
@@ -31218,6 +31223,7 @@
 				E45BA6AA2374926C004DFC07 /* MatchedDeclarationsCache.h in Headers */,
 				FABE72F51059C1EB00D888CC /* MathMLAnnotationElement.h in Headers */,
 				FABE72F51059C1EB00D999DD /* MathMLElement.h in Headers */,
+				E4863CFE23842E9E00972158 /* RuleData.h in Headers */,
 				44A28AAC12DFB8AC00AE923B /* MathMLElementFactory.h in Headers */,
 				0BCF83F71059C1EB00D999DD /* MathMLFractionElement.h in Headers */,
 				FABE72F91059C1EB00D999DD /* MathMLMathElement.h in Headers */,
diff --git a/Source/WebCore/style/RuleData.cpp b/Source/WebCore/style/RuleData.cpp
new file mode 100644
index 0000000..f344db9
--- /dev/null
+++ b/Source/WebCore/style/RuleData.cpp
@@ -0,0 +1,179 @@
+/*
+ * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
+ *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
+ * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
+ * Copyright (C) 2005-2019 Apple Inc. All rights reserved.
+ * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
+ * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
+ * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
+ * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
+ * Copyright (C) Research In Motion Limited 2011. All rights reserved.
+ * Copyright (C) 2012 Google Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#include "config.h"
+#include "RuleData.h"
+
+#include "CSSFontSelector.h"
+#include "CSSKeyframesRule.h"
+#include "CSSSelector.h"
+#include "CSSSelectorList.h"
+#include "HTMLNames.h"
+#include "MediaQueryEvaluator.h"
+#include "SecurityOrigin.h"
+#include "SelectorChecker.h"
+#include "SelectorFilter.h"
+#include "StyleResolver.h"
+#include "StyleRule.h"
+#include "StyleRuleImport.h"
+#include "StyleSheetContents.h"
+#include "ViewportStyleResolver.h"
+
+#if ENABLE(VIDEO_TRACK)
+#include "TextTrackCue.h"
+#endif
+
+namespace WebCore {
+namespace Style {
+
+using namespace HTMLNames;
+
+struct SameSizeAsRuleData {
+    void* a;
+    unsigned b;
+    unsigned c;
+    unsigned d[4];
+};
+
+COMPILE_ASSERT(sizeof(RuleData) == sizeof(SameSizeAsRuleData), RuleData_should_stay_small);
+
+static inline MatchBasedOnRuleHash computeMatchBasedOnRuleHash(const CSSSelector& selector)
+{
+    if (selector.tagHistory())
+        return MatchBasedOnRuleHash::None;
+
+    if (selector.match() == CSSSelector::Tag) {
+        const QualifiedName& tagQualifiedName = selector.tagQName();
+        const AtomString& selectorNamespace = tagQualifiedName.namespaceURI();
+        if (selectorNamespace == starAtom() || selectorNamespace == xhtmlNamespaceURI) {
+            if (tagQualifiedName == anyQName())
+                return MatchBasedOnRuleHash::Universal;
+            return MatchBasedOnRuleHash::ClassC;
+        }
+        return MatchBasedOnRuleHash::None;
+    }
+    if (SelectorChecker::isCommonPseudoClassSelector(&selector))
+        return MatchBasedOnRuleHash::ClassB;
+    if (selector.match() == CSSSelector::Id)
+        return MatchBasedOnRuleHash::ClassA;
+    if (selector.match() == CSSSelector::Class)
+        return MatchBasedOnRuleHash::ClassB;
+    return MatchBasedOnRuleHash::None;
+}
+
+static bool selectorCanMatchPseudoElement(const CSSSelector& rootSelector)
+{
+    const CSSSelector* selector = &rootSelector;
+    do {
+        if (selector->matchesPseudoElement())
+            return true;
+
+        if (const CSSSelectorList* selectorList = selector->selectorList()) {
+            for (const CSSSelector* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
+                if (selectorCanMatchPseudoElement(*subSelector))
+                    return true;
+            }
+        }
+
+        selector = selector->tagHistory();
+    } while (selector);
+    return false;
+}
+
+static inline bool isCommonAttributeSelectorAttribute(const QualifiedName& attribute)
+{
+    // These are explicitly tested for equality in canShareStyleWithElement.
+    return attribute == typeAttr || attribute == readonlyAttr;
+}
+
+static bool computeContainsUncommonAttributeSelector(const CSSSelector& rootSelector, bool matchesRightmostElement = true)
+{
+    const CSSSelector* selector = &rootSelector;
+    do {
+        if (selector->isAttributeSelector()) {
+            // FIXME: considering non-rightmost simple selectors is necessary because of the style sharing of cousins.
+            // It is a primitive solution which disable a lot of style sharing on pages that rely on attributes for styling.
+            // We should investigate better ways of doing this.
+            if (!isCommonAttributeSelectorAttribute(selector->attribute()) || !matchesRightmostElement)
+                return true;
+        }
+
+        if (const CSSSelectorList* selectorList = selector->selectorList()) {
+            for (const CSSSelector* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
+                if (computeContainsUncommonAttributeSelector(*subSelector, matchesRightmostElement))
+                    return true;
+            }
+        }
+
+        if (selector->relation() != CSSSelector::Subselector)
+            matchesRightmostElement = false;
+
+        selector = selector->tagHistory();
+    } while (selector);
+    return false;
+}
+
+static inline PropertyWhitelistType determinePropertyWhitelistType(const CSSSelector* selector)
+{
+    for (const CSSSelector* component = selector; component; component = component->tagHistory()) {
+#if ENABLE(VIDEO_TRACK)
+        if (component->match() == CSSSelector::PseudoElement && (component->pseudoElementType() == CSSSelector::PseudoElementCue || component->value() == TextTrackCue::cueShadowPseudoId()))
+            return PropertyWhitelistCue;
+#endif
+        if (component->match() == CSSSelector::PseudoElement && component->pseudoElementType() == CSSSelector::PseudoElementMarker)
+            return PropertyWhitelistMarker;
+
+        if (const auto* selectorList = selector->selectorList()) {
+            for (const auto* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
+                auto whitelistType = determinePropertyWhitelistType(subSelector);
+                if (whitelistType != PropertyWhitelistNone)
+                    return whitelistType;
+            }
+        }
+    }
+    return PropertyWhitelistNone;
+}
+
+RuleData::RuleData(StyleRule* rule, unsigned selectorIndex, unsigned selectorListIndex, unsigned position)
+    : m_rule(rule)
+    , m_selectorIndex(selectorIndex)
+    , m_selectorListIndex(selectorListIndex)
+    , m_position(position)
+    , m_matchBasedOnRuleHash(static_cast<unsigned>(computeMatchBasedOnRuleHash(*selector())))
+    , m_canMatchPseudoElement(selectorCanMatchPseudoElement(*selector()))
+    , m_containsUncommonAttributeSelector(computeContainsUncommonAttributeSelector(*selector()))
+    , m_linkMatchType(SelectorChecker::determineLinkMatchType(selector()))
+    , m_propertyWhitelistType(determinePropertyWhitelistType(selector()))
+    , m_descendantSelectorIdentifierHashes(SelectorFilter::collectHashes(*selector()))
+{
+    ASSERT(m_position == position);
+    ASSERT(m_selectorIndex == selectorIndex);
+}
+
+} // namespace Style
+} // namespace WebCore
diff --git a/Source/WebCore/style/RuleData.h b/Source/WebCore/style/RuleData.h
new file mode 100644
index 0000000..0125fae
--- /dev/null
+++ b/Source/WebCore/style/RuleData.h
@@ -0,0 +1,93 @@
+/*
+ * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
+ * Copyright (C) 2003-2019 Apple Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ *
+ */
+
+#pragma once
+
+#include "SelectorFilter.h"
+#include "StyleRule.h"
+#include <wtf/text/AtomString.h>
+#include <wtf/text/AtomStringHash.h>
+
+namespace WebCore {
+namespace Style {
+
+enum PropertyWhitelistType {
+    PropertyWhitelistNone   = 0,
+    PropertyWhitelistMarker,
+#if ENABLE(VIDEO_TRACK)
+    PropertyWhitelistCue
+#endif
+};
+
+enum class MatchBasedOnRuleHash : unsigned {
+    None,
+    Universal,
+    ClassA,
+    ClassB,
+    ClassC
+};
+
+class RuleData {
+public:
+    static const unsigned maximumSelectorComponentCount = 8192;
+
+    RuleData(StyleRule*, unsigned selectorIndex, unsigned selectorListIndex, unsigned position);
+
+    unsigned position() const { return m_position; }
+    StyleRule* rule() const { return m_rule.get(); }
+    const CSSSelector* selector() const { return m_rule->selectorList().selectorAt(m_selectorIndex); }
+    unsigned selectorIndex() const { return m_selectorIndex; }
+    unsigned selectorListIndex() const { return m_selectorListIndex; }
+
+    bool canMatchPseudoElement() const { return m_canMatchPseudoElement; }
+    MatchBasedOnRuleHash matchBasedOnRuleHash() const { return static_cast<MatchBasedOnRuleHash>(m_matchBasedOnRuleHash); }
+    bool containsUncommonAttributeSelector() const { return m_containsUncommonAttributeSelector; }
+    unsigned linkMatchType() const { return m_linkMatchType; }
+    PropertyWhitelistType propertyWhitelistType() const { return static_cast<PropertyWhitelistType>(m_propertyWhitelistType); }
+    const SelectorFilter::Hashes& descendantSelectorIdentifierHashes() const { return m_descendantSelectorIdentifierHashes; }
+
+    void disableSelectorFiltering() { m_descendantSelectorIdentifierHashes[0] = 0; }
+
+private:
+    RefPtr<StyleRule> m_rule;
+    unsigned m_selectorIndex : 16;
+    unsigned m_selectorListIndex : 16;
+    // This number was picked fairly arbitrarily. We can probably lower it if we need to.
+    // Some simple testing showed <100,000 RuleData's on large sites.
+    unsigned m_position : 18;
+    unsigned m_matchBasedOnRuleHash : 3;
+    unsigned m_canMatchPseudoElement : 1;
+    unsigned m_containsUncommonAttributeSelector : 1;
+    unsigned m_linkMatchType : 2; //  SelectorChecker::LinkMatchMask
+    unsigned m_propertyWhitelistType : 2;
+    SelectorFilter::Hashes m_descendantSelectorIdentifierHashes;
+};
+
+} // namespace Style
+} // namespace WebCore
+
+namespace WTF {
+
+// RuleData is simple enough that initializing to 0 and moving with memcpy will totally work.
+template<> struct VectorTraits<WebCore::Style::RuleData> : SimpleClassVectorTraits { };
+
+} // namespace WTF
+
diff --git a/Source/WebCore/style/RuleSet.cpp b/Source/WebCore/style/RuleSet.cpp
index 1980f95..d401b67 100644
--- a/Source/WebCore/style/RuleSet.cpp
+++ b/Source/WebCore/style/RuleSet.cpp
@@ -2,7 +2,7 @@
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
- * Copyright (C) 2005-2014 Apple Inc. All rights reserved.
+ * Copyright (C) 2005-2019 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
@@ -53,121 +53,6 @@
 
 using namespace HTMLNames;
 
-// -----------------------------------------------------------------
-
-static inline MatchBasedOnRuleHash computeMatchBasedOnRuleHash(const CSSSelector& selector)
-{
-    if (selector.tagHistory())
-        return MatchBasedOnRuleHash::None;
-
-    if (selector.match() == CSSSelector::Tag) {
-        const QualifiedName& tagQualifiedName = selector.tagQName();
-        const AtomString& selectorNamespace = tagQualifiedName.namespaceURI();
-        if (selectorNamespace == starAtom() || selectorNamespace == xhtmlNamespaceURI) {
-            if (tagQualifiedName == anyQName())
-                return MatchBasedOnRuleHash::Universal;
-            return MatchBasedOnRuleHash::ClassC;
-        }
-        return MatchBasedOnRuleHash::None;
-    }
-    if (SelectorChecker::isCommonPseudoClassSelector(&selector))
-        return MatchBasedOnRuleHash::ClassB;
-    if (selector.match() == CSSSelector::Id)
-        return MatchBasedOnRuleHash::ClassA;
-    if (selector.match() == CSSSelector::Class)
-        return MatchBasedOnRuleHash::ClassB;
-    return MatchBasedOnRuleHash::None;
-}
-
-static bool selectorCanMatchPseudoElement(const CSSSelector& rootSelector)
-{
-    const CSSSelector* selector = &rootSelector;
-    do {
-        if (selector->matchesPseudoElement())
-            return true;
-
-        if (const CSSSelectorList* selectorList = selector->selectorList()) {
-            for (const CSSSelector* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
-                if (selectorCanMatchPseudoElement(*subSelector))
-                    return true;
-            }
-        }
-
-        selector = selector->tagHistory();
-    } while (selector);
-    return false;
-}
-
-static inline bool isCommonAttributeSelectorAttribute(const QualifiedName& attribute)
-{
-    // These are explicitly tested for equality in canShareStyleWithElement.
-    return attribute == typeAttr || attribute == readonlyAttr;
-}
-
-static bool computeContainsUncommonAttributeSelector(const CSSSelector& rootSelector, bool matchesRightmostElement = true)
-{
-    const CSSSelector* selector = &rootSelector;
-    do {
-        if (selector->isAttributeSelector()) {
-            // FIXME: considering non-rightmost simple selectors is necessary because of the style sharing of cousins.
-            // It is a primitive solution which disable a lot of style sharing on pages that rely on attributes for styling.
-            // We should investigate better ways of doing this.
-            if (!isCommonAttributeSelectorAttribute(selector->attribute()) || !matchesRightmostElement)
-                return true;
-        }
-
-        if (const CSSSelectorList* selectorList = selector->selectorList()) {
-            for (const CSSSelector* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
-                if (computeContainsUncommonAttributeSelector(*subSelector, matchesRightmostElement))
-                    return true;
-            }
-        }
-
-        if (selector->relation() != CSSSelector::Subselector)
-            matchesRightmostElement = false;
-
-        selector = selector->tagHistory();
-    } while (selector);
-    return false;
-}
-
-static inline PropertyWhitelistType determinePropertyWhitelistType(const CSSSelector* selector)
-{
-    for (const CSSSelector* component = selector; component; component = component->tagHistory()) {
-#if ENABLE(VIDEO_TRACK)
-        if (component->match() == CSSSelector::PseudoElement && (component->pseudoElementType() == CSSSelector::PseudoElementCue || component->value() == TextTrackCue::cueShadowPseudoId()))
-            return PropertyWhitelistCue;
-#endif
-        if (component->match() == CSSSelector::PseudoElement && component->pseudoElementType() == CSSSelector::PseudoElementMarker)
-            return PropertyWhitelistMarker;
-
-        if (const auto* selectorList = selector->selectorList()) {
-            for (const auto* subSelector = selectorList->first(); subSelector; subSelector = CSSSelectorList::next(subSelector)) {
-                auto whitelistType = determinePropertyWhitelistType(subSelector);
-                if (whitelistType != PropertyWhitelistNone)
-                    return whitelistType;
-            }
-        }
-    }
-    return PropertyWhitelistNone;
-}
-
-RuleData::RuleData(StyleRule* rule, unsigned selectorIndex, unsigned selectorListIndex, unsigned position)
-    : m_rule(rule)
-    , m_selectorIndex(selectorIndex)
-    , m_selectorListIndex(selectorListIndex)
-    , m_position(position)
-    , m_matchBasedOnRuleHash(static_cast<unsigned>(computeMatchBasedOnRuleHash(*selector())))
-    , m_canMatchPseudoElement(selectorCanMatchPseudoElement(*selector()))
-    , m_containsUncommonAttributeSelector(computeContainsUncommonAttributeSelector(*selector()))
-    , m_linkMatchType(SelectorChecker::determineLinkMatchType(selector()))
-    , m_propertyWhitelistType(determinePropertyWhitelistType(selector()))
-    , m_descendantSelectorIdentifierHashes(SelectorFilter::collectHashes(*selector()))
-{
-    ASSERT(m_position == position);
-    ASSERT(m_selectorIndex == selectorIndex);
-}
-
 RuleSet::RuleSet() = default;
 
 RuleSet::~RuleSet() = default;
diff --git a/Source/WebCore/style/RuleSet.h b/Source/WebCore/style/RuleSet.h
index 7fadfa6..3b96581 100644
--- a/Source/WebCore/style/RuleSet.h
+++ b/Source/WebCore/style/RuleSet.h
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
- * Copyright (C) 2003-2014 Apple Inc. All rights reserved.
+ * Copyright (C) 2003-2019 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -21,6 +21,7 @@
 
 #pragma once
 
+#include "RuleData.h"
 #include "RuleFeature.h"
 #include "SelectorCompiler.h"
 #include "SelectorFilter.h"
@@ -33,76 +34,13 @@
 namespace WebCore {
 
 class CSSSelector;
-class ContainerNode;
 class MediaQueryEvaluator;
-class Node;
 class StyleSheetContents;
 
 namespace Style {
 
 class Resolver;
 
-enum PropertyWhitelistType {
-    PropertyWhitelistNone   = 0,
-    PropertyWhitelistMarker,
-#if ENABLE(VIDEO_TRACK)
-    PropertyWhitelistCue
-#endif
-};
-
-enum class MatchBasedOnRuleHash : unsigned {
-    None,
-    Universal,
-    ClassA,
-    ClassB,
-    ClassC
-};
-
-class RuleData {
-public:
-    static const unsigned maximumSelectorComponentCount = 8192;
-
-    RuleData(StyleRule*, unsigned selectorIndex, unsigned selectorListIndex, unsigned position);
-
-    unsigned position() const { return m_position; }
-    StyleRule* rule() const { return m_rule.get(); }
-    const CSSSelector* selector() const { return m_rule->selectorList().selectorAt(m_selectorIndex); }
-    unsigned selectorIndex() const { return m_selectorIndex; }
-    unsigned selectorListIndex() const { return m_selectorListIndex; }
-
-    bool canMatchPseudoElement() const { return m_canMatchPseudoElement; }
-    MatchBasedOnRuleHash matchBasedOnRuleHash() const { return static_cast<MatchBasedOnRuleHash>(m_matchBasedOnRuleHash); }
-    bool containsUncommonAttributeSelector() const { return m_containsUncommonAttributeSelector; }
-    unsigned linkMatchType() const { return m_linkMatchType; }
-    PropertyWhitelistType propertyWhitelistType() const { return static_cast<PropertyWhitelistType>(m_propertyWhitelistType); }
-    const SelectorFilter::Hashes& descendantSelectorIdentifierHashes() const { return m_descendantSelectorIdentifierHashes; }
-
-    void disableSelectorFiltering() { m_descendantSelectorIdentifierHashes[0] = 0; }
-
-private:
-    RefPtr<StyleRule> m_rule;
-    unsigned m_selectorIndex : 16;
-    unsigned m_selectorListIndex : 16;
-    // This number was picked fairly arbitrarily. We can probably lower it if we need to.
-    // Some simple testing showed <100,000 RuleData's on large sites.
-    unsigned m_position : 18;
-    unsigned m_matchBasedOnRuleHash : 3;
-    unsigned m_canMatchPseudoElement : 1;
-    unsigned m_containsUncommonAttributeSelector : 1;
-    unsigned m_linkMatchType : 2; //  SelectorChecker::LinkMatchMask
-    unsigned m_propertyWhitelistType : 2;
-    SelectorFilter::Hashes m_descendantSelectorIdentifierHashes;
-};
-    
-struct SameSizeAsRuleData {
-    void* a;
-    unsigned b;
-    unsigned c;
-    unsigned d[4];
-};
-
-COMPILE_ASSERT(sizeof(RuleData) == sizeof(SameSizeAsRuleData), RuleData_should_stay_small);
-
 class RuleSet {
     WTF_MAKE_NONCOPYABLE(RuleSet); WTF_MAKE_FAST_ALLOCATED;
 public:
@@ -192,10 +130,3 @@
 
 } // namespace Style
 } // namespace WebCore
-
-namespace WTF {
-
-// RuleData is simple enough that initializing to 0 and moving with memcpy will totally work.
-template<> struct VectorTraits<WebCore::Style::RuleData> : SimpleClassVectorTraits { };
-
-} // namespace WTF