Implement a Hit Test Cache.

Source/core/layout/LayoutPart.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. 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
  * License as published by the Free Software Foundation; either
@@ skipping 151 matching lines @@
 
     FrameView* childFrameView = toFrameView(widget());
     LayoutView* childRoot = childFrameView->layoutView();
 
     if (visibleToHitTestRequest(result.hitTestRequest()) && childRoot) {
         LayoutPoint adjustedLocation = accumulatedOffset + location();
         LayoutPoint contentOffset = LayoutPoint(borderLeft() + paddingLeft(), borderTop() + paddingTop()) - LayoutSize(childFrameView->scrollOffset());
         HitTestLocation newHitTestLocation(locationInContainer, -adjustedLocation - contentOffset);
         HitTestRequest newHitTestRequest(result.hitTestRequest().type() | HitTestRequest::ChildFrameHitTest);
         HitTestResult childFrameResult(newHitTestRequest, newHitTestLocation);
+        childFrameResult.setValidityRect(result.validityRect());
 
-        bool isInsideChildFrame = childRoot->hitTest(newHitTestRequest, newHitTestLocation, childFrameResult);
+        bool isInsideChildFrame = childRoot->hitTest(childFrameResult);
 
         if (result.hitTestRequest().listBased())
             result.append(childFrameResult);
         else if (isInsideChildFrame)
             result = childFrameResult;
 
         if (isInsideChildFrame)
             return true;
     }
 
@@ skipping 135 matching lines @@
     if (widget->frameRect() == newFrame)
         return false;
 
     RefPtr<LayoutPart> protector(this);
     RefPtrWillBeRawPtr<Node> protectedNode(node());
     widget->setFrameRect(newFrame);
     return widget->frameRect().size() != newFrame.size();
 }
 
 }