Make ElementShadow::youngestShadowRoot() return a reference

third_party/WebKit/Source/core/dom/ChildFrameDisconnector.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/ChildFrameDisconnector.h"
 
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/html/HTMLFrameOwnerElement.h"
@@ skipping 50 matching lines @@
         HTMLFrameOwnerElement* owner = m_frameOwners[i].get();
         // Don't need to traverse up the tree for the first owner since no
         // script could have moved it.
         if (!i || root().containsIncludingShadowDOM(owner))
             owner->disconnectContentFrame();
     }
 }
 
 void ChildFrameDisconnector::collectFrameOwners(ElementShadow& shadow)
 {
-    for (ShadowRoot* root = shadow.youngestShadowRoot(); root; root = root->olderShadowRoot())
+    for (ShadowRoot* root = &shadow.youngestShadowRoot(); root; root = root->olderShadowRoot())
         collectFrameOwners(*root);
 }
 
 #if ENABLE(ASSERT)
 static unsigned checkConnectedSubframeCountIsConsistent(Node& node)
 {
     unsigned count = 0;
 
     if (node.isElementNode()) {
         if (node.isFrameOwnerElement() && toHTMLFrameOwnerElement(node).contentFrame())
             count++;
 
         if (ElementShadow* shadow = toElement(node).shadow()) {
-            for (ShadowRoot* root = shadow->youngestShadowRoot(); root; root = root->olderShadowRoot())
+            for (ShadowRoot* root = &shadow->youngestShadowRoot(); root; root = root->olderShadowRoot())
                 count += checkConnectedSubframeCountIsConsistent(*root);
         }
     }
 
     for (Node* child = node.firstChild(); child; child = child->nextSibling())
         count += checkConnectedSubframeCountIsConsistent(*child);
 
     // If we undercount there's possibly a security bug since we'd leave frames
     // in subtrees outside the document.
     ASSERT(node.connectedSubframeCount() >= count);
 
     // If we overcount it's safe, but not optimal because it means we'll traverse
     // through the document in ChildFrameDisconnector looking for frames that have
     // already been disconnected.
     ASSERT(node.connectedSubframeCount() == count);
 
     return count;
 }
 #endif
 
 }