Support subtitles for native fullscreen video

Source/core/rendering/RenderLayerModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010, 2012 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 188 matching lines @@
             // to marking entire layers instead. This may sometimes mark more than necessary (when
             // a layer is made of disjoint objects) but in practice is a significant performance
             // savings.
             layer()->addLayerHitTestRects(rects);
         }
     } else {
         RenderObject::addLayerHitTestRects(rects, currentLayer, layerOffset, containerRect);
     }
 }
 
+RenderLayerBacking* RenderLayerModelObject::backing() const
+{
+    return m_layer ? m_layer->backing() : 0;
+}
+
 } // namespace WebCore