Let the WebMediaPlayer decide whether to use overlay video.

Source/core/html/HTMLMediaElement.h

Index: Source/core/html/HTMLMediaElement.h
diff --git a/Source/core/html/HTMLMediaElement.h b/Source/core/html/HTMLMediaElement.h
index 2f1bea3fc8f96c6333f9c3c7361d47bcf86982df..896394ed6106c02c474edc944f7867d90f98eb61 100644
--- a/Source/core/html/HTMLMediaElement.h
+++ b/Source/core/html/HTMLMediaElement.h
@@ -214,6 +214,7 @@ public:
     bool isFullscreen() const;
     void enterFullscreen();
     void exitFullscreen();
+    virtual bool usesOverlayFullscreenVideo() const { return false; }
 
     bool hasClosedCaptions() const;
     bool closedCaptionsVisible() const;
@@ -548,6 +549,8 @@ private:
     bool m_isFinalizing : 1;
     bool m_initialPlayWithoutUserGestures : 1;
     bool m_autoplayMediaCounted : 1;
+    // Whether this element is in overlay fullscreen mode.
+    bool m_inOverlayFullscreenVideo : 1;
 
     PersistentWillBeMember<AudioTrackList> m_audioTracks;
     PersistentWillBeMember<VideoTrackList> m_videoTracks;