Support subtitles for native fullscreen video

Source/core/rendering/RenderLayerCompositor.h

 /*
  * Copyright (C) 2009 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 188 matching lines @@
     void resetTrackedRepaintRects();
     void setTracksRepaints(bool);
 
     void setShouldReevaluateCompositingAfterLayout() { m_reevaluateCompositingAfterLayout = true; }
 
     // Returns all reasons (direct, indirectly due to subtree, and indirectly due to overlap) that a layer should be composited.
     CompositingReasons reasonsForCompositing(const RenderLayer*) const;
 
     virtual String debugName(const GraphicsLayer*) OVERRIDE;
 
+    // Only called for main frame. Input object can be cross frame.
+    void setCurrentFullscreenRenderer(RenderObject*);

[esprehn, 2013/09/13 02:46:07]

This doesn't look safe at all, passing a RenderObject between frames creates
really scary looking conditions where one frame goes through a styleRecalc and
the cleanup is not correct here and now you have a use-after-free.

[trchen, 2013/09/13 05:14:58]

See answer in RLC.cpp

+
 private:
     class OverlapMap;
 
     // GraphicsLayerClient implementation
     virtual void notifyAnimationStarted(const GraphicsLayer*, double) OVERRIDE { }
     virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect&) OVERRIDE;
 
     virtual bool isTrackingRepaints() const OVERRIDE;
 
     // Whether the given RL needs a compositing layer.
@@ skipping 128 matching lines @@
 
     // Layers for overflow controls
     OwnPtr<GraphicsLayer> m_layerForHorizontalScrollbar;
     OwnPtr<GraphicsLayer> m_layerForVerticalScrollbar;
     OwnPtr<GraphicsLayer> m_layerForScrollCorner;
 #if ENABLE(RUBBER_BANDING)
     OwnPtr<GraphicsLayer> m_layerForOverhangAreas;
     OwnPtr<GraphicsLayer> m_layerForOverhangShadow;
 #endif
 
+    RenderObject* m_currentFullscreenRenderer;
+
 #if !LOG_DISABLED
     int m_rootLayerUpdateCount;
     int m_obligateCompositedLayerCount; // count of layer that have to be composited.
     int m_secondaryCompositedLayerCount; // count of layers that have to be composited because of stacking or overlap.
     double m_obligatoryBackingStoreBytes;
     double m_secondaryBackingStoreBytes;
 #endif
 };
 
 
 } // namespace WebCore
 
 #endif // RenderLayerCompositor_h