Add a new App launcher promo to the apps page / NTP.

apps/pref_names.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 "apps/pref_names.h"
 
 namespace apps {
 
 namespace prefs {
 
 // Local state caching knowledge of whether the app launcher is installed.
 const char kAppLauncherIsEnabled[] =
     "apps.app_launcher.should_show_apps_page";
 
 // If set, the user requested to launch the app with this extension id while
 // in Metro mode, and then relaunched to Desktop mode to start it.
 const char kAppLaunchForMetroRestart[] = "apps.app_launch_for_metro_restart";
 
 // Set with |kAppLaunchForMetroRestart|, the profile whose loading triggers
 // launch of the specified app when restarting Chrome in desktop mode.
 const char kAppLaunchForMetroRestartProfile[] =
     "apps.app_launch_for_metro_restart_profile";
 
+// A boolean identifying if we should show the app launcher promo or not.
+const char kShowAppLauncherPromo[] = "app_launcher.show_promo";
+
 }  // namespace prefs
 
 }  // namespace apps