title: Android Alert Dialog with extra background
body: <p>I recently migrated my app to Material Design and I stumbled upon this problem with my Alert Dialogs: </p>
  
  <p><img src="https://i.stack.imgur.com/G9KqO.png" alt="dialog appears to be having two backgrounds and I don&#39;t know how to get rid of the outer background"></p>
  
  <p>I'm applying the dialog style like this: </p>
  
  <p><code>&lt;item name="android:alertDialogTheme"&gt;@style/Theme.AlertDialog&lt;/item&gt;</code> </p>
  
  <p>and <strong>Theme.AlertDialog</strong> looks like this:</p>
  
  <pre><code>&lt;style name="Theme.AlertDialog" parent="Base.V14.Theme.AppCompat.Dialog"&gt;
      &lt;item name="colorPrimary"&gt;@color/theme_primary&lt;/item&gt;
      &lt;item name="colorPrimaryDark"&gt;@color/theme_primary_dark&lt;/item&gt;
      &lt;item name="colorAccent"&gt;@color/theme_accent_dark&lt;/item&gt;
  &lt;/style&gt;
  </code></pre>
  
  <p>This is happening on my Kitkat device and it works fine on Lollipop. Can you help me with getting rid of that outer background?</p>