Abandon prerenders upon render thread shutdown.

third_party/WebKit/public/platform/WebPrerenderingSupport.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 36 matching lines @@
     virtual void add(const WebPrerender&) = 0;
 
     // A prerender is canceled when it is removed from a document.
     virtual void cancel(const WebPrerender&) = 0;
 
     // A prerender is abandoned when it's navigated away from or suspended in the page cache. This
     // is a weaker signal than cancel(), since the launcher hasn't indicated that the prerender isn't
     // wanted, and we may end up using it after, for instance, a short redirect chain.
     virtual void abandon(const WebPrerender&) = 0;
 
+    // The renderer is shutting down, the prerendering layer is not allowed to
+    // access Blink objects after this notification.
+    virtual void detachRenderer() = 0;
+
 protected:
     WebPrerenderingSupport() { }
     virtual ~WebPrerenderingSupport() { }
 
 private:
     static WebPrerenderingSupport* s_platform;
 };
 
 } // namespace blink
 
 #endif // WebPrerenderingSupport_h