Have Frame::tree() return a reference

Source/core/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     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
@@ skipping 348 matching lines @@
             break;
         }
     }
     if (treatment == TreatAsActiveContent) {
         if (Frame* f = frame()) {
             if (!f->loader()->mixedContentChecker()->canRunInsecureContent(m_document->securityOrigin(), url))
                 return false;
         }
     } else if (treatment == TreatAsPassiveContent) {
         if (Frame* f = frame()) {
-            Frame* top = f->tree()->top();
+            Frame* top = f->tree().top();
             if (!top->loader()->mixedContentChecker()->canDisplayInsecureContent(top->document()->securityOrigin(), url))
                 return false;
         }
     } else {
         ASSERT(treatment == TreatAsAlwaysAllowedContent);
     }
     return true;
 }
 
 bool ResourceFetcher::canRequest(Resource::Type type, const KURL& url, const ResourceLoaderOptions& options, bool forPreload)
@@ skipping 245 matching lines @@
     m_documentResources.set(resource->url(), resource);
     return resource;
 }
 
 void ResourceFetcher::determineTargetType(ResourceRequest& request, Resource::Type type)
 {
     ResourceRequest::TargetType targetType;
 
     switch (type) {
     case Resource::MainResource:
-        if (frame()->tree()->parent())
+        if (frame()->tree().parent())
             targetType = ResourceRequest::TargetIsSubframe;
         else
             targetType = ResourceRequest::TargetIsMainFrame;
         break;
     case Resource::XSLStyleSheet:
         ASSERT(RuntimeEnabledFeatures::xsltEnabled());
     case Resource::CSSStyleSheet:
         targetType = ResourceRequest::TargetIsStyleSheet;
         break;
     case Resource::Script:
@@ skipping 675 matching lines @@
 }
 #endif
 
 const ResourceLoaderOptions& ResourceFetcher::defaultResourceOptions()
 {
     DEFINE_STATIC_LOCAL(ResourceLoaderOptions, options, (SendCallbacks, SniffContent, BufferData, AllowStoredCredentials, ClientRequestedCredentials, AskClientForCrossOriginCredentials, DoSecurityCheck, CheckContentSecurityPolicy, UseDefaultOriginRestrictionsForType, DocumentContext));
     return options;
 }
 
 }