Remove //chrome dependency from ExtensionPrefs

chrome/browser/extensions/chrome_extensions_browser_client.cc

 // 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.
 
 #include "chrome/browser/extensions/chrome_extensions_browser_client.h"
 
 #include "apps/common/api/generated_api.h"
 #include "base/command_line.h"
 #include "base/version.h"
 #include "chrome/browser/app_mode/app_mode_utils.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/activity_log/activity_log.h"
+#include "chrome/browser/extensions/api/content_settings/content_settings_service.h"
 #include "chrome/browser/extensions/api/preference/chrome_direct_setting.h"
 #include "chrome/browser/extensions/api/preference/preference_api.h"
 #include "chrome/browser/extensions/api/web_request/web_request_api.h"
 #include "chrome/browser/extensions/chrome_app_sorting.h"
 #include "chrome/browser/extensions/chrome_extension_host_delegate.h"
 #include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/extensions/extension_util.h"
 #include "chrome/browser/external_protocol/external_protocol_handler.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/profiles/profile_manager.h"
@@ skipping 208 matching lines @@
 
   // Generated APIs from lower-level modules.
   extensions::core_api::GeneratedFunctionRegistry::RegisterAll(registry);
   apps::api::GeneratedFunctionRegistry::RegisterAll(registry);
 
   // Generated APIs from Chrome.
   extensions::api::GeneratedFunctionRegistry::RegisterAll(registry);
 #endif
 }
 
+void ChromeExtensionsBrowserClient::AddExtensionPrefsObservers(
+    content::BrowserContext* context,
+    ExtensionPrefs* prefs) const {
+  ContentSettingsService* content_settings =
+      ContentSettingsService::Get(context);
+  prefs->AddObserver(content_settings);
+}
+
 }  // namespace extensions