Let the WebMediaPlayer decide whether to use overlay video.

Source/core/layout/LayoutVideo.cpp

 /*
  * Copyright (C) 2007, 2008, 2009, 2010 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 228 matching lines @@
 
 LayoutUnit LayoutVideo::offsetHeight() const
 {
     if (const LayoutBlock* block = layoutObjectPlaceholder(this))
         return block->offsetHeight();
     return LayoutMedia::offsetHeight();
 }
 
 CompositingReasons LayoutVideo::additionalCompositingReasons() const
 {
-    if (RuntimeEnabledFeatures::overlayFullscreenVideoEnabled()) {
-        HTMLMediaElement* media = toHTMLMediaElement(node());
-        if (media->isFullscreen())
-            return CompositingReasonVideo;
-    }
+    HTMLMediaElement* element = toHTMLMediaElement(node());
+    if (element->isFullscreen() && element->usesOverlayFullscreenVideo())
+        return CompositingReasonVideo;
 
     if (shouldDisplayVideo() && supportsAcceleratedRendering())
         return CompositingReasonVideo;
 
     return CompositingReasonNone;
 }
 
 } // namespace blink