Implement a Hit Test Cache.

Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 796 matching lines @@
     if (!visibleToHitTestRequest(result.hitTestRequest()))
         return false;
 
     HitTestLocation tmpLocation(locationInContainer, -toLayoutSize(accumulatedOffset));
 
     Region regionResult;
     HitTestCulledInlinesGeneratorContext context(regionResult, tmpLocation);
     generateCulledLineBoxRects(context, this);
 
     if (context.intersected()) {
-        updateHitTestResult(result, tmpLocation.point());
+        // TODO(dtapuska): Move the regionResult by accumulatedOffset
+        updateHitTestResult(result, tmpLocation.point(), result.validityRect());
         // We can not use addNodeToListBasedTestResult to determine if we fully enclose the hit-test area
         // because it can only handle rectangular targets.
         result.addNodeToListBasedTestResult(node(), locationInContainer);
         return regionResult.contains(tmpLocation.boundingBox());
     }
     return false;
 }
 
 PositionWithAffinity LayoutInline::positionForPoint(const LayoutPoint& point)
 {
@@ skipping 397 matching lines @@
 {
     // We have to split the parent flow.
     LayoutBlock* newBox = containingBlock()->createAnonymousBlock();
     LayoutBoxModelObject* oldContinuation = continuation();
     setContinuation(newBox);
     LayoutObject* beforeChild = child->nextSibling();
     children()->removeChildNode(this, child);
     splitFlow(beforeChild, newBox, child, oldContinuation);
 }
 
-void LayoutInline::updateHitTestResult(HitTestResult& result, const LayoutPoint& point)
+void LayoutInline::updateHitTestResult(HitTestResult& result, const LayoutPoint& point, const LayoutRect& rect)
 {
     if (result.innerNode())
         return;
 
+    result.intersectValidityRect(rect);
     Node* n = node();
     LayoutPoint localPoint(point);
     if (n) {
         if (isInlineElementContinuation()) {
             // We're in the continuation of a split inline.  Adjust our local point to be in the coordinate space
             // of the principal layoutObject's containing block.  This will end up being the innerNode.
             LayoutBlock* firstBlock = n->layoutObject()->containingBlock();
 
             // Get our containing block.
             LayoutBox* block = containingBlock();
@@ skipping 199 matching lines @@
 }
 
 void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer) const
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer);
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box);
 }
 
 } // namespace blink