Make Event.path() return a pre-calculated NodeList rather than calculating it dynamically.

Source/core/dom/EventRetargeter.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 #include "core/dom/EventRetargeter.h"
 
+#include "RuntimeEnabledFeatures.h"
 #include "core/dom/ContainerNode.h"
 #include "core/dom/EventContext.h"
 #include "core/dom/EventPathWalker.h"
 #include "core/dom/FocusEvent.h"
 #include "core/dom/MouseEvent.h"
 #include "core/dom/Touch.h"
 #include "core/dom/TouchEvent.h"
 #include "core/dom/TouchList.h"
 #include "core/dom/TreeScope.h"
 #include "core/dom/shadow/ShadowRoot.h"
@@ skipping 63 matching lines @@
             return;
         if (!node->isShadowRoot())
             continue;
         if (determineDispatchBehavior(event, toShadowRoot(node), targetStack.last()) == StayInsideShadowDOM)
             return;
         if (!isSVGElement) {
             ASSERT(!targetStack.isEmpty());
             targetStack.removeLast();
         }
     }
+
+    // Calculates eventPath for each node for Event.path() API.
+    if (!RuntimeEnabledFeatures::experimentalShadowDOMEnabled())
+        return;
+    TreeScope* lastScope = 0;
+    size_t eventPathSize = eventPath.size();
+    for (size_t i = 0; i < eventPathSize; ++i) {
+        TreeScope* currentScope = eventPath[i]->node()->treeScope();
+        if (currentScope == lastScope) {
+            // Fast path.
+            eventPath[i]->setEventPath(eventPath[i - 1]->eventPath());
+            continue;
+        }
+        lastScope = currentScope;
+        Vector<RefPtr<Node> > nodes;
+        for (size_t j = 0; j < eventPathSize; ++j) {
+            Node* node = eventPath[j]->node();
+            if (node->treeScope()->isInclusiveAncestorOf(currentScope))
+                nodes.append(node);
+        }
+        eventPath[i]->adoptEventPath(nodes);
+    }
 }
 
 void EventRetargeter::adjustForMouseEvent(Node* node, MouseEvent& mouseEvent)
 {
     adjustForRelatedTarget(node, mouseEvent.relatedTarget(), mouseEvent.eventPath());
 }
 
 void EventRetargeter::adjustForFocusEvent(Node* node, FocusEvent& focusEvent)
 {
     adjustForRelatedTarget(node, focusEvent.relatedTarget(), focusEvent.eventPath());
@@ skipping 126 matching lines @@
             break;
         }
         scope = scope->parentTreeScope();
     }
     for (Vector<TreeScope*, 32>::iterator iter = parentTreeScopes.begin(); iter < parentTreeScopes.end(); ++iter)
         relatedNodeMap.add(*iter, relatedNode);
     return relatedNode;
 }
 
 }