Safely cancel prerenders on threads other than the UI thread

chrome/browser/prerender/prerender_contents.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PRERENDER_PRERENDER_CONTENTS_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_CONTENTS_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 305 matching lines @@
   NotificationRegistrar notification_registrar_;
   TabContentsObserver::Registrar tab_contents_observer_registrar_;
 
   // A vector of URLs that this prerendered page matches against.
   // This array can contain more than element as a result of redirects,
   // such as HTTP redirects or javascript redirects.
   std::vector<GURL> alias_urls_;
 
   bool has_stopped_loading_;
 
+  // This must be the same value as the PrerenderTracker has recorded for
+  // |this|, when |this| has a RenderView.
   FinalStatus final_status_;
 
   bool prerendering_has_started_;
 
   // Time at which we started to load the URL.  This is used to compute
   // the time elapsed from initiating a prerender until the time the
   // (potentially only partially) prerendered page is shown to the user.
   base::TimeTicks load_start_time_;
 
   // Process Metrics of the render process associated with the
   // RenderViewHost for this object.
   scoped_ptr<base::ProcessMetrics> process_metrics_;
 
   // The prerendered TabContents; may be null.
   scoped_ptr<TabContentsWrapper> prerender_contents_;
 
   scoped_ptr<PrerenderRenderViewHostObserver> render_view_host_observer_;
 
   scoped_ptr<TabContentsDelegateImpl> tab_contents_delegate_;
 
+  // These are -1 before a RenderView is created.
+  int child_id_;
+  int route_id_;
+
   DISALLOW_COPY_AND_ASSIGN(PrerenderContents);
 };
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_CONTENTS_H_