[Blink>Media] Add heuristic for dominant video detection for Android

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 9156bba583b6c602b3a8cc84b4db479d0b50a85d..332b08a3148a7f30206a0d445ab1f4748f40953c 100644
--- a/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLMediaElement.cpp
@@ -125,7 +125,8 @@ using DocumentElementSetMap =
 
 namespace {
 
-constexpr float kMostlyFillViewportThreshold = 0.85f;
+constexpr float kMostlyFillViewportThresholdInDominantDimension = 0.85f;
+constexpr float kMostlyFillViewportThresholdForTargetVisibleRatio = 0.75f;
 constexpr double kMostlyFillViewportBecomeStableSeconds = 5;
 constexpr double kCheckViewportIntersectionIntervalSeconds = 1;
 
@@ -4109,9 +4110,10 @@ void HTMLMediaElement::checkViewportIntersectionTimerFired(TimerBase*) {
   // 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());
+
+  bool isMostlyFillingViewport = computeIsMostlyFillingViewport(
+      geometry.targetIntRect(), geometry.rootIntRect(),
+      geometry.intersectionIntRect());
   if (m_mostlyFillingViewport == isMostlyFillingViewport)
     return;
 
@@ -4132,4 +4134,22 @@ void HTMLMediaElement::viewportFillDebouncerTimerFired(TimerBase*) {
     m_webMediaPlayer->becameDominantVisibleContent(m_mostlyFillingViewport);
 }
 
+bool HTMLMediaElement::computeIsMostlyFillingViewport(
+    const IntRect& targetRect,
+    const IntRect& rootRect,
+    const IntRect& intersectionRect) {
+  if (targetRect.size().area() == 0 ||
+      intersectionRect.size().area() <=
+          kMostlyFillViewportThresholdForTargetVisibleRatio *
+              targetRect.size().area()) {
+    return false;
+  }
+
+  float xOccupationRatio = 1.0f * intersectionRect.width() / rootRect.width();
+  float yOccupationRatio = 1.0f * intersectionRect.height() / rootRect.height();

[mlamouri (slow - plz ping), 2017/02/15 11:08:04]

nit: I guess those can be `const float`

[Zhiqiang Zhang (Slow), 2017/02/15 11:52:09]

Done.

+
+  return std::max(xOccupationRatio, yOccupationRatio) >=
+         kMostlyFillViewportThresholdInDominantDimension;
+}
+
 }  // namespace blink