Don't show the apps page on the NTP if the app launcher is installed.

chrome/browser/extensions/app_launcher.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_APP_LAUNCHER_H_
 #define CHROME_BROWSER_EXTENSIONS_APP_LAUNCHER_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 
+class PrefServiceSimple;
+
 namespace extensions {
 
 // Called on the UI thread after determining if the launcher is enabled. A
 // boolean flag is passed, which is true if the app launcher is enabled.
 typedef base::Callback<void(bool)> OnAppLauncherEnabledCompleted;
 
 // Determine whether the app launcher is enabled or not. This may involve a trip
 // to a blocking thread. |completion_callback| is called when an answer is
 // ready. This needs to be called on the UI thread.
-void GetIsAppLauncherEnabled(
+void UpdateIsAppLauncherEnabled(
     const OnAppLauncherEnabledCompleted& completion_callback);
 
+// returns value of pref. 'was app launcher enabled last time i checked'.
+bool IsAppLauncherEnabled();
+
+namespace app_launcher {
+void RegisterPrefs(PrefServiceSimple* pref_service);
+}
+
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_APP_LAUNCHER_H_