Implement a Hit Test Cache.

Source/core/layout/LayoutImage.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011-2012. All rights reserved.
  *
@@ skipping 256 matching lines @@
 
 HTMLMapElement* LayoutImage::imageMap() const
 {
     HTMLImageElement* i = isHTMLImageElement(node()) ? toHTMLImageElement(node()) : 0;
     return i ? i->treeScope().getImageMap(i->fastGetAttribute(usemapAttr)) : 0;
 }
 
 bool LayoutImage::nodeAtPoint(HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction hitTestAction)
 {
     HitTestResult tempResult(result.hitTestRequest(), result.hitTestLocation());
+    tempResult.setValidityRect(result.validityRect());
     bool inside = LayoutReplaced::nodeAtPoint(tempResult, locationInContainer, accumulatedOffset, hitTestAction);
 
     if (!inside && result.hitTestRequest().listBased())
         result.append(tempResult);
     if (inside)
         result = tempResult;
     return inside;
 }
 
 void LayoutImage::layout()
@@ skipping 66 matching lines @@
         return nullptr;
 
     ImageResource* cachedImage = m_imageResource->cachedImage();
     if (cachedImage && cachedImage->image() && cachedImage->image()->isSVGImage())
         return toSVGImage(cachedImage->image())->embeddedContentBox();
 
     return nullptr;
 }
 
 } // namespace blink