We have a problem in the process on destroying WebContentsImpl because

chrome/browser/extensions/api/web_navigation/web_navigation_api.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.
 
 // Defines the Chrome Extensions WebNavigation API functions for observing and
 // intercepting navigation events, as specified in the extension JSON API.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_
 
@@ skipping 87 matching lines @@
       content::RenderViewHost* render_view_host,
       const content::ResourceRedirectDetails& details) OVERRIDE;
   virtual void DidOpenRequestedURL(content::WebContents* new_contents,
                                    const GURL& url,
                                    const content::Referrer& referrer,
                                    WindowOpenDisposition disposition,
                                    content::PageTransition transition,
                                    int64 source_frame_num) OVERRIDE;
   virtual void FrameDetached(content::RenderViewHost* render_view_host,
                              int64 frame_num) OVERRIDE;
-  virtual void WebContentsDestroyed(content::WebContents* tab) OVERRIDE;
+  virtual void WebContentsDestroyed() OVERRIDE;
 
  private:
   explicit WebNavigationTabObserver(content::WebContents* web_contents);
   friend class content::WebContentsUserData<WebNavigationTabObserver>;
 
   // True if the transition and target url correspond to a reference fragment
   // navigation.
   bool IsReferenceFragmentNavigation(FrameNavigationState::FrameID frame_id,
                                      const GURL& url);
 
@@ skipping 133 matching lines @@
 
   // Created lazily upon OnListenerAdded.
   scoped_ptr<WebNavigationEventRouter> web_navigation_event_router_;
 
   DISALLOW_COPY_AND_ASSIGN(WebNavigationAPI);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_WEB_NAVIGATION_WEB_NAVIGATION_API_H_