Merge 126901

Source/WebCore/platform/graphics/skia/OpaqueRegionSkia.cpp

 /*
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 164 matching lines @@
 void OpaqueRegionSkia::pushCanvasLayer(const SkPaint* paint)
 {
     CanvasLayerState state;
     if (paint)
         state.paint = *paint;
     m_canvasLayerStack.append(state);
 }
 
 void OpaqueRegionSkia::popCanvasLayer(const PlatformContextSkia* context)
 {
+    ASSERT(!m_canvasLayerStack.isEmpty());
+    if (m_canvasLayerStack.isEmpty())
+        return;
+
     const CanvasLayerState& canvasLayer = m_canvasLayerStack.last();
     SkRect layerOpaqueRect = canvasLayer.opaqueRect;
     SkPaint layerPaint = canvasLayer.paint;
 
     // Apply the image mask.
     if (canvasLayer.hasImageMask && !layerOpaqueRect.intersect(canvasLayer.imageOpaqueRect))
         layerOpaqueRect.setEmpty();
 
     m_canvasLayerStack.removeLast();
 
@@ skipping 231 matching lines @@
         opaqueRect = vertical;
 }
 
 void OpaqueRegionSkia::markAllAsNonOpaque()
 {
     SkRect& opaqueRect = currentTrackingOpaqueRect(m_opaqueRect, m_canvasLayerStack);
     opaqueRect.setEmpty();
 }
 
 } // namespace WebCore