Detect change on 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 a1f0ce6a74d593703d34135af4a59c9ecdc1652e..a7ea8164553f1584856340c3c17d460b17e5bbf9 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -39,6 +39,7 @@
 #include "core/dom/ElementTraversal.h"
 #include "core/dom/ElementVisibilityObserver.h"
 #include "core/dom/Fullscreen.h"
+#include "core/dom/IntersectionGeometry.h"
 #include "core/dom/TaskRunnerHelper.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/events/Event.h"
@@ -126,6 +127,9 @@ using DocumentElementSetMap =
 
 namespace {
 
+constexpr float kMostlyFillViewportThreshold = 0.85f;
+constexpr double kMostlyFillViewportBecomeStableSeconds = 5;
+
 enum MediaControlsShow {
   MediaControlsShowAttribute = 0,
   MediaControlsShowFullscreen,
@@ -410,6 +414,9 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
       m_playbackProgressTimer(this,
                               &HTMLMediaElement::playbackProgressTimerFired),
       m_audioTracksTimer(this, &HTMLMediaElement::audioTracksTimerFired),
+      m_viewportFillDebouncerTimer(
+          this,
+          &HTMLMediaElement::viewportFillDebouncerTimerFired),
       m_playedTimeRanges(),
       m_asyncEventQueue(GenericEventQueue::create(this)),
       m_playbackRate(1.0f),
@@ -449,6 +456,7 @@ HTMLMediaElement::HTMLMediaElement(const QualifiedName& tagName,
       m_processingPreferenceChange(false),
       m_playingRemotely(false),
       m_inOverlayFullscreenVideo(false),
+      m_mostlyFillingViewport(false),
       m_audioTracks(this, AudioTrackList::create(*this)),
       m_videoTracks(this, VideoTrackList::create(*this)),
       m_textTracks(this, nullptr),
@@ -1192,6 +1200,8 @@ void HTMLMediaElement::startPlayerLoad(const KURL& playerProvidedUrl) {
 
   m_webMediaPlayer->load(loadType(), source, corsMode());
 
+  m_webMediaPlayer->stablyFilledViewport(m_mostlyFillingViewport);
+
   if (isFullscreen()) {
     // This handles any transition to or from fullscreen overlay mode.
     frame->chromeClient().enterFullscreenForElement(this);
@@ -2504,6 +2514,8 @@ void HTMLMediaElement::startPlaybackProgressTimer() {
 }
 
 void HTMLMediaElement::playbackProgressTimerFired(TimerBase*) {
+  checkViewportIntersectionChanged();
+
   if (!std::isnan(m_fragmentEndTime) && currentTime() >= m_fragmentEndTime &&
       getDirectionOfPlayback() == Forward) {
     m_fragmentEndTime = std::numeric_limits<double>::quiet_NaN();
@@ -4193,4 +4205,42 @@ IntRect HTMLMediaElement::AutoplayHelperClientImpl::absoluteBoundingBoxRect()
   return result;
 }
 
+void HTMLMediaElement::checkViewportIntersectionChanged() {
+  // TODO(xjz): Early return if we not in tab mirroring.
+
+  IntersectionGeometry geometry(
+      &document(), this, Vector<Length>(),
+      IntersectionGeometry::ReportRootBounds::kShouldReportRootBounds);
+  geometry.computeGeometry();
+  IntRect intersectRect = geometry.intersectionIntRect();
+  if (m_currentIntersectRect == intersectRect)
+    return;
+
+  m_currentIntersectRect = intersectRect;
+  // Reset on any intersection change, since this indicates the user is
+  // scrolling around in the document, the document is changing layout, etc.
+  m_viewportFillDebouncerTimer.stop();
+  bool isMostlyFillingViewport =
+      (m_currentIntersectRect.size().area() >
+       kMostlyFillViewportThreshold * geometry.rootIntRect().size().area());
+  if (m_mostlyFillingViewport == isMostlyFillingViewport)
+    return;
+
+  if (!isMostlyFillingViewport) {
+    m_mostlyFillingViewport = isMostlyFillingViewport;
+    if (m_webMediaPlayer)
+      m_webMediaPlayer->stablyFilledViewport(m_mostlyFillingViewport);
+    return;
+  }
+
+  m_viewportFillDebouncerTimer.startOneShot(
+      kMostlyFillViewportBecomeStableSeconds, BLINK_FROM_HERE);
+}
+
+void HTMLMediaElement::viewportFillDebouncerTimerFired(TimerBase*) {
+  m_mostlyFillingViewport = true;
+  if (m_webMediaPlayer)
+    m_webMediaPlayer->stablyFilledViewport(m_mostlyFillingViewport);
+}
+
 }  // namespace blink