Implement a Hit Test Cache.

Source/core/layout/LayoutBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. 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 1111 matching lines @@
     if (style()->boxSizing() == BORDER_BOX)
         height -= borderAndPaddingLogicalHeight();
     return std::max(LayoutUnit(), height);
 }
 
 // Hit Testing
 bool LayoutBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction action)
 {
     LayoutPoint adjustedLocation = accumulatedOffset + location();
 
+    LayoutRect boundsRect = borderBoxRect();
+    boundsRect.moveBy(adjustedLocation);
     // Check kids first.
     for (LayoutObject* child = slowLastChild(); child; child = child->previousSibling()) {
         if ((!child->hasLayer() || !toLayoutBoxModelObject(child)->layer()->isSelfPaintingLayer()) && child->nodeAtPoint(result, locationInContainer, adjustedLocation, action)) {
-            updateHitTestResult(result, locationInContainer.point() - toLayoutSize(adjustedLocation));
+            updateHitTestResult(result, locationInContainer.point() - toLayoutSize(adjustedLocation), boundsRect);
             return true;
         }
     }
 
     // Check our bounds next. For this purpose always assume that we can only be hit in the
     // foreground phase (which is true for replaced elements like images).
-    LayoutRect boundsRect = borderBoxRect();
-    boundsRect.moveBy(adjustedLocation);
     if (visibleToHitTestRequest(result.hitTestRequest()) && action == HitTestForeground && locationInContainer.intersects(boundsRect)) {
-        updateHitTestResult(result, locationInContainer.point() - toLayoutSize(adjustedLocation));
+        updateHitTestResult(result, locationInContainer.point() - toLayoutSize(adjustedLocation), boundsRect);
         if (!result.addNodeToListBasedTestResult(node(), locationInContainer, boundsRect))
             return true;
     }
+    result.shrinkValidityRect(boundsRect);
 
     return false;
 }
 
 void LayoutBox::paint(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
     BoxPainter(*this).paint(paintInfo, paintOffset);
 }
 
 
@@ skipping 3635 matching lines @@
 bool LayoutBox::canRenderBorderImage() const
 {
     if (!style()->hasBorder())
         return false;
 
     StyleImage* borderImage = style()->borderImage().image();
     return borderImage && borderImage->canRender(*this, style()->effectiveZoom()) && borderImage->isLoaded();
 }
 
 } // namespace blink