We have a problem in the process on destroying WebContentsImpl because

chrome/browser/ui/tab_contents/core_tab_helper.h

 // 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.
 
 #ifndef CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_
 #define CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_
 
 #include "base/time/time.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
@@ skipping 41 matching lines @@
   int content_restrictions() const { return content_restrictions_; }
 
  private:
   explicit CoreTabHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<CoreTabHelper>;
 
   // content::WebContentsObserver overrides:
   virtual void DidStartLoading(
       content::RenderViewHost* render_view_host) OVERRIDE;
   virtual void WasShown() OVERRIDE;
-  virtual void WebContentsDestroyed(
-      content::WebContents* web_contents) OVERRIDE;
+  virtual void WebContentsDestroyed() OVERRIDE;
   virtual void BeforeUnloadFired(const base::TimeTicks& proceed_time) OVERRIDE;
   virtual void BeforeUnloadDialogCancelled() OVERRIDE;
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
   void OnRequestThumbnailForContextNodeACK(const SkBitmap& bitmap,
                                            const gfx::Size& original_size);
 
   // Delegate for notifying our owner about stuff. Not owned by us.
   CoreTabHelperDelegate* delegate_;
 
@@ skipping 11 matching lines @@
   base::TimeTicks unload_detached_start_time_;
 
   // Content restrictions, used to disable print/copy etc based on content's
   // (full-page plugins for now only) permissions.
   int content_restrictions_;
 
   DISALLOW_COPY_AND_ASSIGN(CoreTabHelper);
 };
 
 #endif  // CHROME_BROWSER_UI_TAB_CONTENTS_CORE_TAB_HELPER_H_