Have Frame::tree() return a reference

Source/core/page/PageGroupLoadDeferrer.cpp

 /*
  * Copyright (C) 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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,
@@ skipping 31 matching lines @@
         if ((deferSelf || otherPage != page)) {
             if (!otherPage->defersLoading()) {
                 m_deferredFrames.append(otherPage->mainFrame());
 
                 // Ensure that we notify the client if the initial empty document is accessed before showing anything
                 // modal, to prevent spoofs while the modal window or sheet is visible.
                 otherPage->mainFrame()->loader()->notifyIfInitialDocumentAccessed();
 
                 // This code is not logically part of load deferring, but we do not want JS code executed beneath modal
                 // windows or sheets, which is exactly when PageGroupLoadDeferrer is used.
-                for (Frame* frame = otherPage->mainFrame(); frame; frame = frame->tree()->traverseNext())
+                for (Frame* frame = otherPage->mainFrame(); frame; frame = frame->tree().traverseNext())
                     frame->document()->suspendScheduledTasks();
             }
         }
     }
 
     size_t count = m_deferredFrames.size();
     for (size_t i = 0; i < count; ++i)
         if (Page* page = m_deferredFrames[i]->page())
             page->setDefersLoading(true);
 }
 
 PageGroupLoadDeferrer::~PageGroupLoadDeferrer()
 {
     for (size_t i = 0; i < m_deferredFrames.size(); ++i) {
         if (Page* page = m_deferredFrames[i]->page()) {
             page->setDefersLoading(false);
 
-            for (Frame* frame = page->mainFrame(); frame; frame = frame->tree()->traverseNext())
+            for (Frame* frame = page->mainFrame(); frame; frame = frame->tree().traverseNext())
                 frame->document()->resumeScheduledTasks();
         }
     }
 }
 
 
 } // namespace WebCore