[Panels] Fix crash when killing panel extension from TaskManager.

chrome/browser/task_manager/task_manager_resource_providers.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 "chrome/browser/task_manager/task_manager_resource_providers.h"
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/bind.h"
@@ skipping 694 matching lines @@
           break;
         }
       }
       break;
     }
     case content::NOTIFICATION_WEB_CONTENTS_DISCONNECTED:
     {
       for (PanelResourceMap::iterator iter = resources_.begin();
            iter != resources_.end(); ++iter) {
         Panel* panel = iter->first;
-        if (!panel->GetWebContents()) {
+        WebContents* panel_contents = panel->GetWebContents();
+        if (!panel_contents || panel_contents == web_contents) {
           Remove(panel);
           break;
         }
       }
       break;
     }
     default:
       NOTREACHED() << "Unexpected notificiation.";
       break;
   }
@@ skipping 1143 matching lines @@
     case content::NOTIFICATION_WEB_CONTENTS_CONNECTED:
       Add(web_contents->GetRenderViewHost());
       break;
     case content::NOTIFICATION_WEB_CONTENTS_DISCONNECTED:
       Remove(web_contents->GetRenderViewHost());
       break;
     default:
       NOTREACHED() << "Unexpected notification.";
   }
 }