Add the about_page key to shared_module manifest

chrome/common/extensions/chrome_manifest_handlers.cc

 // Copyright (c) 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/common/extensions/chrome_manifest_handlers.h"
 
 #include "chrome/common/extensions/api/bluetooth/bluetooth_manifest_handler.h"
 #include "chrome/common/extensions/api/commands/commands_handler.h"
 #include "chrome/common/extensions/api/extension_action/browser_action_handler.h"
 #include "chrome/common/extensions/api/extension_action/page_action_handler.h"
@@ skipping 50 matching lines @@
   (new InputComponentsHandler)->Register();
 #endif
   (new ManagedModeHandler)->Register();
   (new MediaGalleriesHandlerParser)->Register();
   (new MimeTypesHandlerParser)->Register();
   (new MinimumChromeVersionChecker)->Register();
   (new NaClModulesHandler)->Register();
   (new OAuth2ManifestHandler)->Register();
   (new OmniboxHandler)->Register();
   (new OptionsPageHandler)->Register();
+  (new AboutPageHandler)->Register();
   (new PageActionHandler)->Register();
   (new PluginsHandler)->Register();
   (new RequirementsHandler)->Register();  // Depends on plugins.
   (new SettingsOverridesHandler)->Register();
   (new SocketsManifestHandler)->Register();
   (new SpellcheckHandler)->Register();
   (new StorageSchemaManifestHandler)->Register();
   (new SystemIndicatorHandler)->Register();
   (new ThemeHandler)->Register();
   (new TtsEngineManifestHandler)->Register();
   (new UIOverridesHandler)->Register();
   (new UpdateURLHandler)->Register();
   (new UrlHandlersParser)->Register();
   (new URLOverridesHandler)->Register();
 #endif
 }
 
 }  // namespace extensions