Monitor the intersection of video and viewport.

third_party/WebKit/Source/core/html/HTMLMediaElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
index 56ad755a6e9c9743151d0a62dc99d5335758bdd9..4c0909ac5bd21c2e6a2ece6edb22b02c66d69e1f 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -464,8 +464,7 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
       m_autoplayHelper(
           AutoplayExperimentHelper::create(m_autoplayHelperClient.get())),
       m_autoplayUmaHelper(AutoplayUmaHelper::create(this)),
-      m_remotePlaybackClient(nullptr),
-      m_autoplayVisibilityObserver(nullptr) {
+      m_remotePlaybackClient(nullptr) {
   ThreadState::current()->registerPreFinalizer(this);
 
   BLINK_MEDIA_LOG << "HTMLMediaElement(" << (void*)this << ")";
@@ -482,6 +481,11 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
   addElementToDocumentMap(this, &document);
 
   UseCounter::count(document, UseCounter::HTMLMediaElement);
+
+  m_videoViewportRatioObserver = new ElementViewportRatioObserver(
+      this, WTF::bind(&HTMLMediaElement::onVideoViewportRatioChanged,
+                      wrapWeakPersistent(this)));
+  m_videoViewportRatioObserver->start();
 }
 
 HTMLMediaElement::~HTMLMediaElement() {
@@ -497,6 +501,8 @@ HTMLMediaElement::~HTMLMediaElement() {
 void HTMLMediaElement::dispose() {
   closeMediaSource();
 
+  m_videoViewportRatioObserver->stop();
+
   // Destroying the player may cause a resource load to be canceled,
   // which could result in LocalDOMWindow::dispatchWindowLoadEvent() being
   // called via ResourceFetch::didLoadResource(), then
@@ -1723,16 +1729,7 @@ void HTMLMediaElement::setReadyState(ReadyState state) {
       if (!isGestureNeededForPlayback()) {
         if (isHTMLVideoElement() && muted() &&
             RuntimeEnabledFeatures::autoplayMutedVideosEnabled()) {
-          // We might end up in a situation where the previous
-          // observer didn't had time to fire yet. We can avoid
-          // creating a new one in this case.
-          if (!m_autoplayVisibilityObserver) {
-            m_autoplayVisibilityObserver = new ElementVisibilityObserver(
-                this,
-                WTF::bind(&HTMLMediaElement::onVisibilityChangedForAutoplay,
-                          wrapWeakPersistent(this)));
-            m_autoplayVisibilityObserver->start();
-          }
+          m_shouldAutoplayWhenVisible = true;
         } else {
           m_paused = false;
           invalidateCachedTime();
@@ -2355,7 +2352,7 @@ void HTMLMediaElement::setMuted(bool muted) {
 
   bool wasAutoplayingMuted =
       !paused() && m_muted && isLockedPendingUserGesture();
-  bool wasPendingAutoplayMuted = m_autoplayVisibilityObserver && paused() &&
+  bool wasPendingAutoplayMuted = m_shouldAutoplayWhenVisible && paused() &&
                                  m_muted && isLockedPendingUserGesture();
 
   if (UserGestureIndicator::processingUserGesture())
@@ -2382,11 +2379,9 @@ void HTMLMediaElement::setMuted(bool muted) {
   }
 
   // If an element was a candidate for autoplay muted but not visible, it will
-  // have a visibility observer ready to start its playback.
-  if (wasPendingAutoplayMuted) {
-    m_autoplayVisibilityObserver->stop();
-    m_autoplayVisibilityObserver = nullptr;
-  }
+  // start its playback once becomes visible.
+  if (wasPendingAutoplayMuted)
+    m_shouldAutoplayWhenVisible = false;
 }
 
 void HTMLMediaElement::updateVolume() {
@@ -3742,7 +3737,7 @@ DEFINE_TRACE(HTMLMediaElement) {
   visitor->trace(m_autoplayHelper);
   visitor->trace(m_autoplayUmaHelper);
   visitor->trace(m_srcObject);
-  visitor->trace(m_autoplayVisibilityObserver);
+  visitor->trace(m_videoViewportRatioObserver);
   visitor->template registerWeakMembers<HTMLMediaElement,
                                         &HTMLMediaElement::clearWeakMembers>(
       this);
@@ -3968,8 +3963,15 @@ EnumerationHistogram& HTMLMediaElement::showControlsHistogram() const {
   return histogram;
 }
 
-void HTMLMediaElement::onVisibilityChangedForAutoplay(bool isVisible) {
-  if (!isVisible)
+void HTMLMediaElement::onVideoViewportRatioChanged(float ratio) {
+  if (m_webMediaPlayer) {
+    m_webMediaPlayer->videoViewportRatioChanged(ratio);
+  }
+  m_viewportRatio = ratio;
+  bool isVisible = ratio > 0.f;
+  m_autoplayUmaHelper->visibilityMaybeChangedforMutedVideo(isVisible);
+
+  if (!isVisible || !m_shouldAutoplayWhenVisible)
     return;
 
   if (shouldAutoplay()) {
@@ -3981,13 +3983,7 @@ void HTMLMediaElement::onVisibilityChangedForAutoplay(bool isVisible) {
 
     updatePlayState();
   }
-
-  // TODO(zqzhang): There's still flaky leak if onVisibilityChangedForAutoplay()
-  // is never called.  The leak comes from either ElementVisibilityObserver or
-  // IntersectionObserver. Should keep an eye on it.  See
-  // https://crbug.com/627539
-  m_autoplayVisibilityObserver->stop();
-  m_autoplayVisibilityObserver = nullptr;
+  m_shouldAutoplayWhenVisible = false;
 }
 
 void HTMLMediaElement::clearWeakMembers(Visitor* visitor) {