title: Custom dialog hasn't divider under the title
body: <p>At the official documentation there is an article of how to create <a href="http://developer.android.com/guide/topics/ui/dialogs.html" rel="nofollow noreferrer">custom dialogs</a>. And there is also a picture of result dialog which have gradient border under it's title.</p>
  <p>When I copy this code to run it on my machine and look at the results I get the dialog without
  gradient divider between the dialog's title and it's content:</p>
  <p><img src="https://i.stack.imgur.com/CHjIM.png" alt="enter image description here" /></p>
  <p>Is this normal behavior and if it is, tell me how can I add divider by myself through the code, or using styles mechanism?</p>