Switch Extensions::TabHelper to use WebContents, WebContentsUserData.

chrome/browser/sessions/tab_restore_service.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/sessions/tab_restore_service.h"
 
 #include <algorithm>
 #include <iterator>
 #include <map>
 
@@ skipping 524 matching lines @@
   tab->current_navigation_index = controller->GetCurrentEntryIndex();
   if (tab->current_navigation_index == -1 && entry_count > 0)
     tab->current_navigation_index = 0;
   tab->tabstrip_index = index;
 
   TabContents* tab_contents =
       TabContents::FromWebContents(controller->GetWebContents());
   // tab_contents is NULL in some browser tests.
   if (tab_contents) {
     const extensions::Extension* extension =
-        tab_contents->extension_tab_helper()->extension_app();
+        extensions::TabHelper::FromWebContents(controller->GetWebContents())->
+            extension_app();
     if (extension)
       tab->extension_app_id = extension->id();
   }
 
   tab->user_agent_override =
       controller->GetWebContents()->GetUserAgentOverride();
 
   // TODO(ajwong): This does not correctly handle storage for isolated apps.
   tab->session_storage_namespace =
       controller->GetDefaultSessionStorageNamespace();
@@ skipping 696 matching lines @@
   // the front, not the end and we just added the entries to the end).
   entries_to_write_ = staging_entries_.size();
 
   PruneEntries();
   NotifyTabsChanged();
 }
 
 Time TabRestoreService::TimeNow() const {
   return time_factory_ ? time_factory_->TimeNow() : Time::Now();
 }