Make event.composedPath() on window behave the same way as that on document

third_party/WebKit/Source/core/events/EventPath.cpp

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 366 matching lines @@
 
     RelatedTargetMap relatedNodeMap;
     buildRelatedNodeMap(*targetNode, relatedNodeMap);
     for (size_t j = 0; j < treeScopes.size(); ++j) {
       adjustedTouchList[j]->append(touch.cloneWithNewTarget(
           findRelatedNode(*treeScopes[j], relatedNodeMap)));
     }
   }
 }
 
-const NodeEventContext& EventPath::topNodeEventContext() {
+NodeEventContext& EventPath::topNodeEventContext() {
   DCHECK(!isEmpty());
   return last();
 }
 
 void EventPath::ensureWindowEventContext() {
   DCHECK(m_event);
   if (!m_windowEventContext)
     m_windowEventContext =
         new WindowEventContext(*m_event, topNodeEventContext());
 }
@@ skipping 12 matching lines @@
 
 DEFINE_TRACE(EventPath) {
   visitor->trace(m_nodeEventContexts);
   visitor->trace(m_node);
   visitor->trace(m_event);
   visitor->trace(m_treeScopeEventContexts);
   visitor->trace(m_windowEventContext);
 }
 
 }  // namespace blink