Merge 113677 - [chromium] Viewport is not filled when out of texture memory on mac

Source/WebCore/platform/graphics/chromium/cc/CCOcclusionTracker.h

 /*
  * Copyright (C) 2012 Google 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
@@ skipping 59 matching lines @@
     // Report operations for recording overdraw metrics.
     CCOverdrawMetrics& overdrawMetrics() const { return *m_overdrawMetrics.get(); }
 
     // FIXME: Remove this when paint tracking is on for paint culling.
     void setUsePaintTracking(bool use) { m_usePaintTracking = use; }
 
     // FIXME: Remove these in future, they are to make CLs for transitioning to this easier.
     const Region& currentOcclusionInScreenSpace() const;
     const Region& currentOcclusionInTargetSurface() const;
 
+    // Gives the region of the screen that is not occluded by something opaque.
+    Region computeVisibleRegionInScreen() const { return subtract(Region(m_scissorRectInScreenSpace), m_stack.last().occlusionInScreen); }
+
 protected:
     struct StackObject {
         StackObject() : surface(0) { }
         StackObject(const RenderSurfaceType* surface) : surface(surface) { }
         const RenderSurfaceType* surface;
         Region occlusionInScreen;
         Region occlusionInTarget;
     };
 
     // The stack holds occluded regions for subtrees in the RenderSurface-Layer tree, so that when we leave a subtree we may
@@ skipping 12 matching lines @@
     IntRect m_scissorRectInScreenSpace;
     OwnPtr<CCOverdrawMetrics> m_overdrawMetrics;
     bool m_usePaintTracking; // FIXME: Remove this when paint tracking is on for paint culling.
 };
 
 typedef CCOcclusionTrackerBase<LayerChromium, RenderSurfaceChromium> CCOcclusionTracker;
 typedef CCOcclusionTrackerBase<CCLayerImpl, CCRenderSurface> CCOcclusionTrackerImpl;
 
 }
 #endif // CCOcclusionTracker_h