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..b531897046e449d0076ad5a31481b00d028e3af0 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"
@@ -2526,6 +2527,30 @@ void HTMLMediaElement::playbackProgressTimerFired(TimerBase*) {
     mediaControls()->playbackProgressed();
 
   cueTimeline().updateActiveCues(currentTime());
+
+  if (m_webMediaPlayer) {

[miu, 2016/11/21 21:07:03]

There's an early return from this method about 6-8 lines above. But we want this
to always execute. So, please move this up (perhaps to the very top of this
method?).

[xjz, 2016/11/21 23:58:42]

Done. Moved this to the very top of the method.

+    // Check whether the intersection with viewport has changed.
+    ExecutionContext* context = getExecutionContext();
+    DCHECK(context->isDocument());
+    Document& document = toDocument(*context);
+    IntersectionGeometry geometry(&document, this, Vector<Length>(), true);
+    geometry.computeGeometry();
+    WebRect intersectRect =
+        WebRect(geometry.intersectionRect().x().rawValue(),

[miu, 2016/11/21 21:07:04]

This translation between rectangle data types is a functional detail that
belongs in IntersectionGeometry more than it does here in HTMLMediaElement. Can
you change intersectionRect() and rootRect() to return a WebRect? If not, maybe
you could create two accessor methods in IntersectionGeometry:
intersectionWebRect() and rootWebRect()?

[xjz, 2016/11/21 23:58:42]

Done. Add accessor methods in IntersectionGeometry.

+                geometry.intersectionRect().y().rawValue(),
+                geometry.intersectionRect().width().rawValue(),
+                geometry.intersectionRect().height().rawValue());
+    if (m_currentViewportIntersection.intersectRect != intersectRect) {
+      m_currentViewportIntersection.intersectRect = intersectRect;
+      m_currentViewportIntersection.rootRect =
+          WebRect(geometry.rootRect().x().rawValue(),
+                  geometry.rootRect().y().rawValue(),
+                  geometry.rootRect().width().rawValue(),
+                  geometry.rootRect().height().rawValue());
+      m_webMediaPlayer->videoViewportIntersectionChanged(
+          m_currentViewportIntersection);
+    }
+  }
 }
 
 void HTMLMediaElement::scheduleTimeupdateEvent(bool periodicEvent) {