title: How to make DropdownButtonFormField support multiple line text?
body: <p>A have a <code>DropdownButtonFormField</code> which show long text as one of the item. The long text able to show in multiple line on dropdown.</p>
  <p><a href="https://i.stack.imgur.com/yrXem.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/yrXem.jpg" alt="drop down" /></a></p>
  <p>However after it is selected, only 1 line of text is shown. The second line become hidden.
  <a href="https://i.stack.imgur.com/sVqWy.jpg" rel="noreferrer"><img src="https://i.stack.imgur.com/sVqWy.jpg" alt="selected" /></a></p>
  <pre><code>String _selectedState = '';
  List&lt;String&gt; _stateList = ['a very very long long long long long text'];
  
                  DropdownButtonFormField&lt;String&gt;(
                    isExpanded: true,
                    value: _selectedState,
                    onChanged: (state) {
                     
                    },                     
                    items: _stateList
                        .map&lt;DropdownMenuItem&lt;String&gt;&gt;((String value) {
                      return DropdownMenuItem&lt;String&gt;(
                        value: value,
                        child: Text(value),
                      );
                    }).toList(),
                  ),
  </code></pre>
  <p>How to solve this?</p>