title: Cannot see my chromecast in Guest Mode
body: <p>I have created a sample Android application just to see the "Google Cast" button on Action Bar and a list of ChromeCast devices when I press it. I did everything according to "Android Sender App Development" document. Now I do see my ChromeCast device when we are on same WiFi, but if I switch on my phone to another WIFi, I don't see my ChromeCast as a "nearby device". I did turned on a flag "Supports Google Cast Guest Mode" on "Google Cast SDK Developer console" for my application. What I am missing?
  Here is the code in my activity:</p>
  
  <pre><code>@Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.layout_main);
  
      mMediaRouter = MediaRouter.getInstance(getApplicationContext());
      mMediaRouteSelector = new MediaRouteSelector.Builder()
          .addControlCategory(CastMediaControlIntent.categoryForCast(MY_APP_ID))
          .build();   
  }
  
  @Override
  protected void onResume() {
      super.onResume();
      mMediaRouterCallback = new MyMediaRouterCallback();
      mMediaRouter.addCallback(mMediaRouteSelector, mMediaRouterCallback,
                  MediaRouter.CALLBACK_FLAG_REQUEST_DISCOVERY); 
  }
  
  @Override
  protected void onPause() {
      if (isFinishing()) 
          mMediaRouter.removeCallback(mMediaRouterCallback);
      super.onPause();
  }
  
  @Override
  public boolean onCreateOptionsMenu(Menu menu) {
      super.onCreateOptionsMenu(menu);
  
      getMenuInflater().inflate(R.menu.cast, menu);
      MenuItem mediaRouteMenuItem = menu.findItem(R.id.media_route_menu_item);
      MediaRouteActionProvider mediaRouteActionProvider = (MediaRouteActionProvider) MenuItemCompat
              .getActionProvider(mediaRouteMenuItem);
      mediaRouteActionProvider.setRouteSelector(mMediaRouteSelector);
  
      return true;
  
  }
  </code></pre>