Include viewport visibility checks for autoplay experiment.

third_party/WebKit/Source/core/layout/LayoutView.cpp

Index: third_party/WebKit/Source/core/layout/LayoutView.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutView.cpp b/third_party/WebKit/Source/core/layout/LayoutView.cpp
index aa3ccf3f2599d681445a8a682a191d7b98273321..abb0c2cd2e5c0f779882692664a1c00481c8ef37 100644
--- a/third_party/WebKit/Source/core/layout/LayoutView.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutView.cpp
@@ -28,10 +28,12 @@
 #include "core/frame/Settings.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/html/HTMLIFrameElement.h"
+#include "core/html/HTMLVideoElement.h"
 #include "core/inspector/InspectorTraceEvents.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutFlowThread.h"
 #include "core/layout/LayoutGeometryMap.h"
+#include "core/layout/LayoutMedia.h"
 #include "core/layout/LayoutPart.h"
 #include "core/layout/LayoutQuote.h"
 #include "core/layout/LayoutScrollbarPart.h"
@@ -954,4 +956,24 @@ void LayoutView::willBeDestroyed()
     m_compositor.clear();
 }
 
+void LayoutView::registerMediaForPositionChangeNotification(LayoutMedia* media)

[esprehn, 2015/10/01 07:04:15]

reference

[liberato (no reviews please), 2015/10/01 22:49:03]

done, though the vector must still be LayoutMedia* and the callers now send
*this.  why is reference preferable here?

+{
+    if (!m_mediaForPositionNotification.contains(media))
+        m_mediaForPositionNotification.append(media);
+}
+
+void LayoutView::unregisterMediaForPositionChangeNotification(LayoutMedia* media)

[esprehn, 2015/10/01 07:04:15]

reference

[liberato (no reviews please), 2015/10/01 22:49:03]

ditto.

+{
+    size_t at = m_mediaForPositionNotification.find(media);
+    if (at != kNotFound)
+        m_mediaForPositionNotification.remove(at);
+}
+
+void LayoutView::sendMediaPositionChangeNotifications()
+{
+    for (auto& media : m_mediaForPositionNotification) {
+        media->notifyPositionMayHaveChanged();

[esprehn, 2015/10/01 07:04:15]

This isn't really the same timing as intersection observer, it would be on a
Timer, I think we should do that for this too otherwise you'll depend on the
synchronous dispatch which is bad

[liberato (no reviews please), 2015/10/01 22:49:03]

One of the objections to a prior iteration of this CL was setting timers too
often on scroll events.  those events happen less often than
sendMediaPositionChangeNotification() is called now.

plus, the callback does most of the real work on a (debounced) timer anyway. 
i'll leave it for now.  i believe it will work with the IntersectionObserver as
is.

+    }
+}
+
 } // namespace blink