Add test to track the number of hit tests on various events

Source/core/testing/Internals.idl

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 49 matching lines @@
     [RaisesException] boolean isValidContentSelect(Element contentElement);
     [RaisesException] Node treeScopeRootNode(Node node);
     [RaisesException] Node parentTreeScope(Node node);
     [RaisesException] boolean hasSelectorForIdInShadow(Element host, DOMString id);
     [RaisesException] boolean hasSelectorForClassInShadow(Element host, DOMString className);
     [RaisesException] boolean hasSelectorForAttributeInShadow(Element host, DOMString attributeName);
     [RaisesException] boolean hasSelectorForPseudoClassInShadow(Element host, DOMString pseudoClass);
     [RaisesException] unsigned short compareTreeScopePosition(Node treeScope1, Node treeScope2);
     [RaisesException] unsigned long updateStyleAndReturnAffectedElementCount();
     [RaisesException] unsigned long needsLayoutCount();
+    [RaisesException] unsigned long hitTestCountDelta(Document document);
 
     // CSS Animation and Transition testing.
     unsigned long numberOfActiveAnimations();
     [RaisesException] void pauseAnimations(double pauseTime);
 
     [RaisesException] Node nextSiblingByWalker(Node node);
     [RaisesException] Node firstChildByWalker(Node node);
     [RaisesException] Node lastChildByWalker(Node node);
     [RaisesException] Node nextNodeByWalker(Node node);
     [RaisesException] Node previousNodeByWalker(Node node);
@@ skipping 196 matching lines @@
     [RaisesException] boolean ignoreLayoutWithPendingStylesheets(Document document);
 
     // These functions are for testing NetInfo. You must call setNetworkStateNotifierTestOnly(true)
     // before calling setNetworkConnectionInfo.
     void setNetworkStateNotifierTestOnly(boolean testOnly);
     [RaisesException] void setNetworkConnectionInfo(DOMString type);
 
     // This function is for testing HitRegions on Canvas2D.
     unsigned long countHitRegions(CanvasRenderingContext2D context);
 };