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

third_party/WebKit/Source/core/page/ChromeClient.cpp

 /*
  * Copyright (C) 2006, 2007, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2012, Samsung Electronics. All rights reserved.
  *
  * 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.
  *
@@ skipping 49 matching lines @@
 
   // Constrain the window position within the valid screen area.
   window.SetX(std::max(screen.X(),
                        std::min(window.X(), screen.MaxX() - window.Width())));
   window.SetY(std::max(screen.Y(),
                        std::min(window.Y(), screen.MaxY() - window.Height())));
   SetWindowRect(window, frame);
 }
 
 bool ChromeClient::CanOpenModalIfDuringPageDismissal(
-    Frame* main_frame,
+    Frame& main_frame,
     ChromeClient::DialogType dialog,
     const String& message) {
-  for (Frame* frame = main_frame; frame; frame = frame->Tree().TraverseNext()) {
+  for (Frame* frame = &main_frame; frame;
+       frame = frame->Tree().TraverseNext()) {
     if (!frame->IsLocalFrame())
       continue;
     LocalFrame& local_frame = ToLocalFrame(*frame);
     Document::PageDismissalType dismissal =
         local_frame.GetDocument()->PageDismissalEventBeingDispatched();
     if (dismissal != Document::kNoDismissal) {
       return ShouldOpenModalDialogDuringPageDismissal(local_frame, dialog,
                                                       message, dismissal);
     }
   }
@@ skipping 149 matching lines @@
   // Suspend pages in case the client method runs a new event loop that would
   // otherwise cause the load to continue while we're in the middle of
   // executing JavaScript.
   ScopedPageSuspender suspender;
 
   PrintDelegate(frame);
   return true;
 }
 
 }  // namespace blink