Lazy evaluation of event.path by numbering TreeScopes in DFS order for later O(1) queries

Source/core/events/NodeEventContext.h

 /*
  * Copyright (C) 2014 Google 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 29 matching lines @@
 
 class NodeEventContext {
 public:
     // FIXME: Use ContainerNode instead of Node.
     NodeEventContext(PassRefPtr<Node>, PassRefPtr<EventTarget> currentTarget);
     ~NodeEventContext();
 
     Node* node() const { return m_node.get(); }
 
     void setTreeScopeEventContext(PassRefPtr<TreeScopeEventContext> prpTreeScopeEventContext) { m_treeScopeEventContext = prpTreeScopeEventContext; }
+    TreeScopeEventContext* treeScopeEventContext() { return m_treeScopeEventContext.get(); }
 
     EventTarget* target() const { return m_treeScopeEventContext->target(); }
     EventTarget* relatedTarget() const { return m_treeScopeEventContext->relatedTarget(); }
     TouchEventContext* touchEventContext() const { return m_treeScopeEventContext->touchEventContext(); }
-    PassRefPtr<NodeList> eventPath() const { return m_treeScopeEventContext->eventPath(); }
 
     bool currentTargetSameAsTarget() const { return m_currentTarget.get() == target(); }
     void handleLocalEvents(Event*) const;
 
 private:
     RefPtr<Node> m_node;
     RefPtr<EventTarget> m_currentTarget;
     RefPtr<TreeScopeEventContext> m_treeScopeEventContext;
 };
 
 }
 
 #endif // NodeEventContext_h