Implement a Hit Test Cache.

Source/core/paint/DeprecatedPaintLayerStackingNode.cpp

Index: Source/core/paint/DeprecatedPaintLayerStackingNode.cpp
diff --git a/Source/core/paint/DeprecatedPaintLayerStackingNode.cpp b/Source/core/paint/DeprecatedPaintLayerStackingNode.cpp
index 25b2fbac73fb1aaaeabe3d35e7233def7d6abb35..8557a3ef347e2a44f2e4d7fc7de20c0b19fc5447 100644
--- a/Source/core/paint/DeprecatedPaintLayerStackingNode.cpp
+++ b/Source/core/paint/DeprecatedPaintLayerStackingNode.cpp
@@ -340,21 +340,20 @@ LayoutBoxModelObject* DeprecatedPaintLayerStackingNode::layoutObject() const
 
 bool DeprecatedPaintLayerStackingNode::hitTest(HitTestResult& result)
 {
-    return hitTest(result.hitTestRequest(), result.hitTestLocation(), result);
-}
-
-bool DeprecatedPaintLayerStackingNode::hitTest(const HitTestRequest& request, const HitTestLocation& hitTestLocation, HitTestResult& result)
-{
     ASSERT(layer()->isSelfPaintingLayer() || layer()->hasSelfPaintingLayerDescendant());
 
     // LayoutView should make sure to update layout before entering hit testing
     ASSERT(!layoutObject()->frame()->view()->layoutPending());
     ASSERT(!layoutObject()->document().layoutView()->needsLayout());
 
+    const HitTestRequest& request = result.hitTestRequest();
+    const HitTestLocation& hitTestLocation = result.hitTestLocation();
+
     // Start with frameVisibleRect to ensure we include the scrollbars.
     LayoutRect hitTestArea = frameVisibleRect(layoutObject());
     if (request.ignoreClipping())
         hitTestArea.unite(LayoutRect(layoutObject()->view()->documentRect()));
+    result.setValidityRect(boundingRect(hitTestLocation.point()));
 
     DeprecatedPaintLayer* insideLayer = layer()->hitTestLayer(layer(), 0, result, hitTestArea, hitTestLocation, false);
     if (!insideLayer) {