Compositor hit test performance improvement

Source/core/rendering/RenderObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 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 1004 matching lines @@
     void postDestroy();
 
     virtual bool canBeReplacedWithInlineRunIn() const;
 
     virtual void insertedIntoTree();
     virtual void willBeRemovedFromTree();
 
     void setDocumentForAnonymous(Document* document) { ASSERT(isAnonymous()); m_node = document; }
 
     // Add hit-test rects for the render tree rooted at this node to the provided collection on a
-    // per-RenderLayer basis. CurrentLayer must be the enclosing layer,
-    // and layerOffset is the current offset within this layer. Subclass implementations will add
-    // any offset for this renderer within it's container, so callers should provide only the
-    // offset of the container within it's layer.
-    virtual void addLayerHitTestRects(LayerHitTestRects&, const RenderLayer* currentLayer, const LayoutPoint& layerOffset) const;
+    // per-RenderLayer basis.
+    // currentLayer must be the enclosing layer, and layerOffset is the current offset within
+    // this layer. Subclass implementations will add any offset for this renderer within it's
+    // container, so callers should provide only the offset of the container within it's layer.
+    // containerRect is a rect that has already been added for the currentLayer which is likely to
+    // be a container for child elements. Any rect wholly contained by containerRect can be
+    // skipped.
+    virtual void addLayerHitTestRects(LayerHitTestRects&, const RenderLayer* currentLayer, const LayoutPoint& layerOffset, const LayoutRect& containerRect) const;
 
     // Add hit-test rects for this renderer only to the provided list. layerOffset is the offset
     // of this renderer within the current layer that should be used for each result.
     virtual void computeSelfHitTestRects(Vector<LayoutRect>&, const LayoutPoint& layerOffset) const { };
 
 private:
     RenderFlowThread* locateFlowThreadContainingBlock() const;
     void removeFromRenderFlowThread();
     void removeFromRenderFlowThreadRecursive(RenderFlowThread*);
 
@@ skipping 352 matching lines @@
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const WebCore::RenderObject*);
 void showLineTree(const WebCore::RenderObject*);
 void showRenderTree(const WebCore::RenderObject* object1);
 // We don't make object2 an optional parameter so that showRenderTree
 // can be called from gdb easily.
 void showRenderTree(const WebCore::RenderObject* object1, const WebCore::RenderObject* object2);
 #endif
 
 #endif // RenderObject_h