Use const ref for LocalFrame::LocalFrameRoot and FrameTree::Top

third_party/WebKit/Source/core/frame/LocalFrame.h

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999-2001 Lars Knoll <knoll@kde.org>
  *                     1999-2001 Antti Koivisto <koivisto@kde.org>
  *                     2000-2001 Simon Hausmann <hausmann@kde.org>
  *                     2000-2001 Dirk Mueller <mueller@kde.org>
  *                     2000 Stefan Schimanski <1Stein@gmx.de>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights
  * reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 136 matching lines @@
   FrameSelection& Selection() const;
   InputMethodController& GetInputMethodController() const;
   ScriptController& GetScriptController() const;
   SpellChecker& GetSpellChecker() const;
   FrameConsole& Console() const;
 
   // This method is used to get the highest level LocalFrame in this
   // frame's in-process subtree.
   // FIXME: This is a temporary hack to support RemoteFrames, and callers
   // should be updated to avoid storing things on the main frame.
-  LocalFrame* LocalFrameRoot();
+  LocalFrame& LocalFrameRoot() const;
 
   // Note that the result of this function should not be cached: a frame is
   // not necessarily detached when it is navigated, so the return value can
   // change.
   // In addition, this function will always return true for a detached frame.
   // TODO(dcheng): Move this to LocalDOMWindow and figure out the right
   // behavior for detached windows.
   bool IsCrossOriginSubframe() const;
 
   CoreProbeSink* InstrumentingAgents() { return instrumenting_agents_.Get(); }
@@ skipping 209 matching lines @@
   explicit ScopedFrameBlamer(LocalFrame*);
   ~ScopedFrameBlamer();
 
  private:
   Member<LocalFrame> frame_;
 };
 
 }  // namespace blink
 
 #endif  // LocalFrame_h