title: setCloseButtonIcon() method doesn't change default Close button
body: <p>I try to change default icon for Close Button in Chrome custom tabs (CustomTabsIntent.Builder)</p>
  
  <p>Simple code for testing:</p>
  
  <pre><code>Bitmap closeIcon = BitmapFactory.decodeResource(getResources(), R.mipmap.ic_launcher);
  intentBuilder.setCloseButtonIcon(closeIcon);
  </code></pre>
  
  <p>But nothing happens. Why? (Nexus 7, Marshmallow)</p>