Cleanup: Remove unneeded forward declarations from chrome/browser/extensions.

chrome/browser/extensions/settings/settings_frontend.h

 // Copyright (c) 2011 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_SETTINGS_SETTINGS_FRONTEND_H_
 #define CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_FRONTEND_H_
 #pragma once
 
+#include <string>
+
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list_threadsafe.h"
 #include "chrome/browser/extensions/settings/settings_leveldb_storage.h"
 #include "chrome/browser/extensions/settings/settings_observer.h"
 #include "chrome/browser/sync/api/syncable_service.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
-class FilePath;
 class Profile;
 
 namespace extensions {
 
 class SettingsStorage;
 
 // The component of extension settings which runs on the UI thread, as opposed
 // to SettingsBackend which lives on the FILE thread.
 // All public methods must be called on the UI thread.
 class SettingsFrontend {
@@ skipping 64 matching lines @@
   // Ref-counted container for the SettingsBackend object.
   class Core;
   scoped_refptr<Core> core_;
 
   DISALLOW_COPY_AND_ASSIGN(SettingsFrontend);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SETTINGS_SETTINGS_FRONTEND_H_