Upgrade old app host to new app launcher on startup

This patch is a continuation of https://codereview.chromium.org/16805002/.

BUG=248825

Review URL: https://chromiumcodereview.appspot.com/17022015

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@209604 0039d316-1c4b-4281-b951-d872f2087c98
  static AppListController* GetInstance() {
    return Singleton<AppListController,
                     LeakySingletonTraits<AppListController> >::get();
  }

  static AppListController* GetInstance() {
    return Singleton<AppListController,
                     LeakySingletonTraits<AppListController> >::get();
  }
