app_shell: Fix PrefsTabHelper dependency of ExtensionHost

chrome/browser/extensions/chrome_extensions_browser_client.h

 // Copyright 2013 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_EXTENSIONS_CHROME_EXTENSIONS_BROWSER_CLIENT_H_
 #define CHROME_BROWSER_EXTENSIONS_CHROME_EXTENSIONS_BROWSER_CLIENT_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/lazy_instance.h"
@@ skipping 32 matching lines @@
   virtual content::BrowserContext* GetOffTheRecordContext(
       content::BrowserContext* context) OVERRIDE;
   virtual content::BrowserContext* GetOriginalContext(
       content::BrowserContext* context) OVERRIDE;
   virtual PrefService* GetPrefServiceForContext(
       content::BrowserContext* context) OVERRIDE;
   virtual bool DeferLoadingBackgroundHosts(
       content::BrowserContext* context) const OVERRIDE;
   virtual bool IsBackgroundPageAllowed(
       content::BrowserContext* context) const OVERRIDE;
+  virtual void OnExtensionHostCreated(content::WebContents* web_contents)
+      OVERRIDE;
   virtual bool DidVersionUpdate(content::BrowserContext* context) OVERRIDE;
   virtual scoped_ptr<AppSorting> CreateAppSorting() OVERRIDE;
   virtual bool IsRunningInForcedAppMode() OVERRIDE;
   virtual content::JavaScriptDialogManager* GetJavaScriptDialogManager()
       OVERRIDE;
 
  private:
   friend struct base::DefaultLazyInstanceTraits<ChromeExtensionsBrowserClient>;
 
   // Observer for Chrome-specific notifications.
   ChromeNotificationObserver notification_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeExtensionsBrowserClient);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_CHROME_EXTENSIONS_BROWSER_CLIENT_H_