We have a problem in the process on destroying WebContentsImpl because

content/public/browser/web_contents_observer.cc

 // Copyright (c) 2012 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.
 
 #include "content/public/browser/web_contents_observer.h"
 
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/render_view_host.h"
 
@@ skipping 43 matching lines @@
   return web_contents_->Send(message);
 }
 
 int WebContentsObserver::routing_id() const {
   if (!web_contents_)
     return MSG_ROUTING_NONE;
 
   return web_contents_->GetRoutingID();
 }
 
-void WebContentsObserver::WebContentsImplDestroyed() {
-  // Do cleanup so that 'this' can safely be deleted from WebContentsDestroyed.
-  web_contents_->RemoveObserver(this);
-  WebContentsImpl* contents = web_contents_;
-  web_contents_ = NULL;
-  WebContentsDestroyed(contents);
-}
-
 }  // namespace content