Have Frame::tree() return a reference

Source/core/dom/FullscreenElementStack.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 153 matching lines @@
         // is not an ancestor of the context object. (NOTE: Ignore this requirement if the request was
         // made via the legacy Mozilla-style API.)
         if (!m_fullScreenElementStack.isEmpty() && !inLegacyMozillaMode) {
             Element* lastElementOnStack = m_fullScreenElementStack.last().get();
             if (lastElementOnStack == element || !lastElementOnStack->contains(element))
                 break;
         }
 
         // A descendant browsing context's document has a non-empty fullscreen element stack.
         bool descendentHasNonEmptyStack = false;
-        for (Frame* descendant = document()->frame() ? document()->frame()->tree()->traverseNext() : 0; descendant; descendant = descendant->tree()->traverseNext()) {
+        for (Frame* descendant = document()->frame() ? document()->frame()->tree().traverseNext() : 0; descendant; descendant = descendant->tree().traverseNext()) {
             if (fullscreenElementFrom(descendant->document())) {
                 descendentHasNonEmptyStack = true;
                 break;
             }
         }
         if (descendentHasNonEmptyStack && !inLegacyMozillaMode)
             break;
 
         // This algorithm is not allowed to show a pop-up:
         //   An algorithm is allowed to show a pop-up if, in the task in which the algorithm is running, either:
@@ skipping 93 matching lines @@
     Document* currentDoc = document();
 
     // 2. If doc's fullscreen element stack is empty, terminate these steps.
     if (m_fullScreenElementStack.isEmpty())
         return;
 
     // 3. Let descendants be all the doc's descendant browsing context's documents with a non-empty fullscreen
     // element stack (if any), ordered so that the child of the doc is last and the document furthest
     // away from the doc is first.
     Deque<RefPtr<Document> > descendants;
-    for (Frame* descendant = document()->frame() ?  document()->frame()->tree()->traverseNext() : 0; descendant; descendant = descendant->tree()->traverseNext()) {
+    for (Frame* descendant = document()->frame() ?  document()->frame()->tree().traverseNext() : 0; descendant; descendant = descendant->tree().traverseNext()) {
         if (fullscreenElementFrom(descendant->document()))
             descendants.prepend(descendant->document());
     }
 
     // 4. For each descendant in descendants, empty descendant's fullscreen element stack, and queue a
     // task to fire an event named fullscreenchange with its bubbles attribute set to true on descendant.
     for (Deque<RefPtr<Document> >::iterator i = descendants.begin(); i != descendants.end(); ++i) {
         from(i->get())->clearFullscreenElementStack();
         addDocumentToFullScreenChangeEventQueue(i->get());
     }
@@ skipping 257 matching lines @@
         if (!target)
             target = fullscreen->webkitCurrentFullScreenElement();
     }
 
     if (!target)
         target = doc;
     m_fullScreenChangeEventTargetQueue.append(target);
 }
 
 } // namespace WebCore