Have Frame::tree() return a reference

Source/core/rendering/HitTestResult.cpp

 /*
  * Copyright (C) 2006, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2012 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 183 matching lines @@
 
 Frame* HitTestResult::targetFrame() const
 {
     if (!m_innerURLElement)
         return 0;
 
     Frame* frame = m_innerURLElement->document().frame();
     if (!frame)
         return 0;
 
-    return frame->tree()->find(m_innerURLElement->target());
+    return frame->tree().find(m_innerURLElement->target());
 }
 
 bool HitTestResult::isSelected() const
 {
     if (!m_innerNonSharedNode)
         return false;
 
     if (Frame* frame = m_innerNonSharedNode->document().frame())
         return frame->selection().contains(m_hitTestLocation.point());
     return false;
@@ skipping 290 matching lines @@
 {
     for (Node* node = m_innerNode.get(); node; node = NodeRenderingTraversal::parent(node)) {
         if (node->isElementNode())
             return toElement(node);
     }
 
     return 0;
 }
 
 } // namespace WebCore