Split ExtensionSystem interface from ExtensionSystemImpl implementation, part 1.

chrome/browser/extensions/api/preference/preference_api.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/extensions/api/preference/preference_api.h"
 
 #include <map>
 #include <utility>
 
 #include "base/lazy_instance.h"
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/extensions/api/preference/preference_api_constants.h"
 #include "chrome/browser/extensions/api/preference/preference_helpers.h"
 #include "chrome/browser/extensions/api/proxy/proxy_api.h"
 #include "chrome/browser/extensions/extension_service.h"
-#include "chrome/browser/extensions/extension_system.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/notification_details.h"
 #include "content/public/browser/notification_source.h"
 #include "extensions/browser/extension_pref_value_map.h"
 #include "extensions/browser/extension_pref_value_map_factory.h"
 #include "extensions/browser/extension_prefs_factory.h"
+#include "extensions/browser/extension_system.h"
 #include "extensions/browser/pref_names.h"
 #include "extensions/common/error_utils.h"
 #include "extensions/common/permissions/api_permission.h"
 
 namespace keys = extensions::preference_api_constants;
 namespace helpers = extensions::preference_helpers;
 
 using base::DictionaryValue;
 
 namespace extensions {
@@ skipping 690 matching lines @@
   std::string browser_pref;
   if (!ValidateBrowserPref(pref_key, &browser_pref))
     return false;
 
   PreferenceAPI::Get(GetProfile())
       ->RemoveExtensionControlledPref(extension_id(), browser_pref, scope);
   return true;
 }
 
 }  // namespace extensions