Have Frame::tree() return a reference

Source/core/editing/SpellChecker.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 77 matching lines @@
 bool SpellChecker::isContinuousSpellCheckingEnabled() const
 {
     return editorClient().isContinuousSpellCheckingEnabled();
 }
 
 void SpellChecker::toggleContinuousSpellChecking()
 {
     editorClient().toggleContinuousSpellChecking();
     if (isContinuousSpellCheckingEnabled())
         return;
-    for (Frame* frame = m_frame.page()->mainFrame(); frame && frame->document(); frame = frame->tree()->traverseNext()) {
+    for (Frame* frame = m_frame.page()->mainFrame(); frame && frame->document(); frame = frame->tree().traverseNext()) {
         for (Node* node = frame->document()->rootNode(); node; node = NodeTraversal::next(node)) {
             node->setAlreadySpellChecked(false);
         }
     }
 }
 
 bool SpellChecker::isGrammarCheckingEnabled()
 {
     return editorClient().isGrammarCheckingEnabled();
 }
@@ skipping 758 matching lines @@
 }
 
 void SpellChecker::requestTextChecking(const Element& element)
 {
     RefPtr<Range> rangeToCheck = rangeOfContents(const_cast<Element*>(&element));
     m_spellCheckRequester->requestCheckingFor(SpellCheckRequest::create(TextCheckingTypeSpelling | TextCheckingTypeGrammar, TextCheckingProcessBatch, rangeToCheck, rangeToCheck));
 }
 
 
 } // namespace WebCore