title: AdRequest.Builder.addKeyword() is not working
body: <p>I have some problem about adMob for targeting purposes.
  I've read the google adMob reference guide for AdRequest.
  They recommended to use addKeyword for targeting purposes.
  But I couldn't see the targeting ads. I can see only Not targeting ads.
  Please let me know what is problem on my code.</p>
  
  <pre><code>AdRequest.Builder adRequestBuilder = new AdRequest.Builder().addKeyword("game");
  mAdLoader.loadAd(adRequestBuilder.build());
  </code></pre>
  
  <p>Can not This targeting ads be shown on test device?
  Is it working on real market app and user device?</p>