title: android:windowBackground not working
body: <p>I have created a custom dialog theme like so:</p>
  
  <pre><code>&lt;style name="dialogLight" parent="Theme.AppCompat.Light.Dialog"&gt;
      &lt;item name="android:windowBackground"&gt;attr/theme_dialogBackground&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>However when I then run the app, the <code>dialog</code> background is its default (transparent on one device and black on another).</p>
  
  <p>However if I change <code>android:windowBackground</code> to <code>android:background</code>, the correct behaviour for <code>android:background</code> is seen, and the default background of all the views in the dialog becomes the specified value, as it should.</p>
  
  <p>Changing the value of android:windowBackground to an @drawable or an @color work as they should.</p>
  
  <p>I know what the difference between <code>android:windowBackground</code> and <code>android:background</code> is, and using <code>android:background</code> is not what I need, as I only want the window background colour to change.</p>
  
  <p>So why is <code>android:windowBackground</code> not being applied?</p>