How should I customize DropdownButtons and DropdownMenuItems in Flutter? : <p>The default <a href="https://docs.flutter.io/flutter/material/DropdownButton-class.html" rel="noreferrer">DropdownButton</a> with DropdownMenuItems returns a light-grey dropdown. How should I customize the dropdown (e.g. background color, dropdown width)? I can change the <code>style</code> property in both DropdownButton and DropdownMenuItem, like this:</p>

<pre><code>return new DropdownButton(
      value: ...,
      items: ...,
      onChanged: ...,
      style: new TextStyle(
        color: Colors.white,
      ),
    );
</code></pre>

<p>but this doesn't change the dropdown's background color.</p>

<p>Should I copy DropdownMenu and extend it? Does Flutter plan to add customization for this widget in the near future?</p>
