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

Source/core/events/NodeEventContext.h

Index: Source/core/events/NodeEventContext.h
diff --git a/Source/core/events/NodeEventContext.h b/Source/core/events/NodeEventContext.h
index 4a8cf0cecd03014d3458a971a6100019d0a3247b..d01f84974a148b7cdfefcaa9c54ca2043996ef67 100644
--- a/Source/core/events/NodeEventContext.h
+++ b/Source/core/events/NodeEventContext.h
@@ -47,11 +47,11 @@ public:
     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;