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

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 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 140 matching lines @@
           kSecurityMessageSource, kErrorMessageLevel,
           "Blocked opening '" +
               request.GetResourceRequest().Url().ElidedString() +
               "' in a new window because the request was made in a sandboxed "
               "frame whose 'allow-popups' permission is not set."));
       return nullptr;
     }
 
     if (opener_frame.GetSettings() &&
         !opener_frame.GetSettings()->GetSupportsMultipleWindows())
-      window = opener_frame.Tree().Top();
+      window = &opener_frame.Tree().Top();
   }
 
   if (window) {
     // JS can run inside reuseExistingWindow (via onblur), which can detach
     // the target window.
     if (!window->Client())
       return nullptr;
     if (request.GetShouldSetOpener() == kMaybeSetOpener)
       window->Client()->SetOpener(&opener_frame);
     return window;
@@ skipping 120 matching lines @@
   }
 
   // TODO(japhet): Form submissions on RemoteFrames don't work yet.
   FrameLoadRequest new_request(0, request.GetResourceRequest());
   new_request.SetForm(request.Form());
   if (new_frame->IsLocalFrame())
     ToLocalFrame(new_frame)->Loader().Load(new_request);
 }
 
 }  // namespace blink