Implement a Hit Test Cache.

Source/core/layout/LayoutBox.cpp

Index: Source/core/layout/LayoutBox.cpp
diff --git a/Source/core/layout/LayoutBox.cpp b/Source/core/layout/LayoutBox.cpp
index 3fe7409b4b57cf3135ad63f77991de306704d548..f5e8ffba67f4a84f2db842693c7adbf9933bfd57 100644
--- a/Source/core/layout/LayoutBox.cpp
+++ b/Source/core/layout/LayoutBox.cpp
@@ -1129,23 +1129,24 @@ bool LayoutBox::nodeAtPoint(HitTestResult& result, const HitTestLocation& locati
 {
     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;
 }