diff --git a/Source/WebCore/ChangeLog b/Source/WebCore/ChangeLog
index e999c8c..00b3b16 100644
--- a/Source/WebCore/ChangeLog
+++ b/Source/WebCore/ChangeLog
@@ -1,3 +1,22 @@
+2019-10-22  Peng Liu  <peng.liu6@apple.com>
+
+        [Picture-in-Picture Web API] The implementation needs runtime logging
+        https://bugs.webkit.org/show_bug.cgi?id=202774
+
+        Reviewed by Eric Carlson.
+
+        Add runtime logging, no new tests needed.
+
+        * Modules/pictureinpicture/HTMLVideoElementPictureInPicture.cpp:
+        (WebCore::HTMLVideoElementPictureInPicture::HTMLVideoElementPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::~HTMLVideoElementPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::requestPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::exitPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::didEnterPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::didExitPictureInPicture):
+        (WebCore::HTMLVideoElementPictureInPicture::logChannel const):
+        * Modules/pictureinpicture/HTMLVideoElementPictureInPicture.h:
+
 2019-10-22  Yusuke Suzuki  <ysuzuki@apple.com>
 
         [JSC] Remove non-LargeAllocation restriction for JSCallee
diff --git a/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.cpp b/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.cpp
index df960b2..735e403 100644
--- a/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.cpp
+++ b/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.cpp
@@ -31,6 +31,7 @@
 
 #include "HTMLVideoElement.h"
 #include "JSDOMPromiseDeferred.h"
+#include "Logging.h"
 #include "PictureInPictureWindow.h"
 #include "VideoTrackList.h"
 #include <wtf/IsoMallocInlines.h>
@@ -41,12 +42,18 @@
 
 HTMLVideoElementPictureInPicture::HTMLVideoElementPictureInPicture(HTMLVideoElement& videoElement)
     : m_videoElement(videoElement)
+#if !RELEASE_LOG_DISABLED
+    , m_logger(videoElement.document().logger())
+    , m_logIdentifier(uniqueLogIdentifier())
+#endif
 {
+    ALWAYS_LOG(LOGIDENTIFIER);
     m_videoElement.setPictureInPictureObserver(this);
 }
 
 HTMLVideoElementPictureInPicture::~HTMLVideoElementPictureInPicture()
 {
+    ALWAYS_LOG(LOGIDENTIFIER);
     m_videoElement.setPictureInPictureObserver(nullptr);
 }
 
@@ -64,36 +71,36 @@
 void HTMLVideoElementPictureInPicture::requestPictureInPicture(HTMLVideoElement& videoElement, Ref<DeferredPromise>&& promise)
 {
     if (!videoElement.player() || !videoElement.player()->supportsPictureInPicture()) {
-        promise->reject(NotSupportedError);
+        promise->reject(NotSupportedError, "The video element does not support the Picture-in-Picture mode.");
         return;
     }
 
     if (videoElement.readyState() == HTMLMediaElementEnums::HAVE_NOTHING) {
-        promise->reject(InvalidStateError);
+        promise->reject(InvalidStateError, "The video element is not ready to enter the Picture-in-Picture mode.");
         return;
     }
 
 #if ENABLE(VIDEO_TRACK)
     if (!videoElement.videoTracks() || !videoElement.videoTracks()->length()) {
-        promise->reject(InvalidStateError);
+        promise->reject(InvalidStateError, "The video element does not have a video track or it has not detected a video track yet.");
         return;
     }
 #endif
 
     bool userActivationRequired = !videoElement.document().pictureInPictureElement();
     if (userActivationRequired && !UserGestureIndicator::processingUserGesture()) {
-        promise->reject(NotAllowedError);
+        promise->reject(NotAllowedError, "The request is not triggered by a user activation.");
         return;
     }
 
     if (videoElement.document().pictureInPictureElement() == &videoElement) {
-        promise->reject(NotAllowedError);
+        promise->reject(NotAllowedError, "The video element is already in the Picture-in-Picture mode.");
         return;
     }
 
     auto videoElementPictureInPicture = HTMLVideoElementPictureInPicture::from(videoElement);
     if (videoElementPictureInPicture->m_enterPictureInPicturePromise || videoElementPictureInPicture->m_exitPictureInPicturePromise) {
-        promise->reject(NotAllowedError);
+        promise->reject(NotAllowedError, "The video element is processing a Picture-in-Picture request.");
         return;
     }
 
@@ -101,7 +108,7 @@
         videoElementPictureInPicture->m_enterPictureInPicturePromise = WTFMove(promise);
         videoElement.webkitSetPresentationMode(HTMLVideoElement::VideoPresentationMode::PictureInPicture);
     } else
-        promise->reject(NotSupportedError);
+        promise->reject(NotSupportedError, "The video element does not support the Picture-in-Picture mode.");
 }
 
 bool HTMLVideoElementPictureInPicture::autoPictureInPicture(HTMLVideoElement& videoElement)
@@ -126,6 +133,7 @@
 
 void HTMLVideoElementPictureInPicture::exitPictureInPicture(Ref<DeferredPromise>&& promise)
 {
+    INFO_LOG(LOGIDENTIFIER);
     if (m_enterPictureInPicturePromise || m_exitPictureInPicturePromise) {
         promise->reject(NotAllowedError);
         return;
@@ -137,6 +145,7 @@
 
 void HTMLVideoElementPictureInPicture::didEnterPictureInPicture()
 {
+    INFO_LOG(LOGIDENTIFIER);
     m_videoElement.document().setPictureInPictureElement(&m_videoElement);
     if (m_enterPictureInPicturePromise) {
         m_enterPictureInPicturePromise->resolve();
@@ -146,6 +155,7 @@
 
 void HTMLVideoElementPictureInPicture::didExitPictureInPicture()
 {
+    INFO_LOG(LOGIDENTIFIER);
     m_videoElement.document().setPictureInPictureElement(nullptr);
     if (m_exitPictureInPicturePromise) {
         m_exitPictureInPicturePromise->resolve();
@@ -153,6 +163,13 @@
     }
 }
 
+#if !RELEASE_LOG_DISABLED
+WTFLogChannel& HTMLVideoElementPictureInPicture::logChannel() const
+{
+    return LogMedia;
+}
+#endif
+
 } // namespace WebCore
 
 #endif // ENABLE(PICTURE_IN_PICTURE_API)
diff --git a/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.h b/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.h
index 5311c02..292830b 100644
--- a/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.h
+++ b/Source/WebCore/Modules/pictureinpicture/HTMLVideoElementPictureInPicture.h
@@ -31,6 +31,7 @@
 #include "PictureInPictureObserver.h"
 #include "Supplementable.h"
 #include <wtf/IsoMalloc.h>
+#include <wtf/LoggerHelper.h>
 
 namespace WebCore {
 
@@ -40,7 +41,11 @@
 
 class HTMLVideoElementPictureInPicture
     : public Supplement<HTMLVideoElement>
-    , public PictureInPictureObserver {
+    , public PictureInPictureObserver
+#if !RELEASE_LOG_DISABLED
+    , private LoggerHelper
+#endif
+{
     WTF_MAKE_ISO_ALLOCATED(HTMLVideoElementPictureInPicture);
 public:
     HTMLVideoElementPictureInPicture(HTMLVideoElement&);
@@ -58,6 +63,13 @@
     void didEnterPictureInPicture();
     void didExitPictureInPicture();
 
+#if !RELEASE_LOG_DISABLED
+    const Logger& logger() const final { return m_logger.get(); }
+    const void* logIdentifier() const final { return m_logIdentifier; }
+    const char* logClassName() const final { return "HTMLVideoElementPictureInPicture"; }
+    WTFLogChannel& logChannel() const final;
+#endif
+
 private:
     static const char* supplementName() { return "HTMLVideoElementPictureInPicture"; }
 
@@ -67,6 +79,11 @@
     HTMLVideoElement& m_videoElement;
     RefPtr<DeferredPromise> m_enterPictureInPicturePromise;
     RefPtr<DeferredPromise> m_exitPictureInPicturePromise;
+
+#if !RELEASE_LOG_DISABLED
+    Ref<const Logger> m_logger;
+    const void* m_logIdentifier;
+#endif
 };
 
 } // namespace WebCore