title: Missing scrollbar in ScrollViewer containing ItemsControl
body: <p>I want my <code>ItemsControl</code> to have an automatic vertical scrollbar when the content doesn't fit. I've added a <code>ScrollViewer</code> around it but it doesn't show the scrollbar and instead makes the items not wrap at all.</p>
  
  <pre><code>&lt;ScrollViewer HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Auto"&gt;
  &lt;ItemsControl ItemsSource="{Binding RecipientsNames}"&gt;
      &lt;ItemsControl.ItemsPanel&gt;
          &lt;ItemsPanelTemplate&gt;
              &lt;WrapPanel/&gt;
          &lt;/ItemsPanelTemplate&gt;
      &lt;/ItemsControl.ItemsPanel&gt;
      &lt;ItemsControl.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;Button x:Name="btnContact" Click="BtnContact_Click"
                      Width="Auto" Height="14" Padding="0" BorderThickness="0" Margin="0 0 6 0" HorizontalAlignment="Left" VerticalAlignment="Top"&gt;
                  &lt;TextBlock Text="{Binding Path=Name}" FontSize="12" Margin="0 -2 0 -2"/&gt;
              &lt;/Button&gt;
          &lt;/DataTemplate&gt;
      &lt;/ItemsControl.ItemTemplate&gt;
  &lt;/ItemsControl&gt;
  &lt;/ScrollViewer&gt;
  </code></pre>
  
  <p>I've also tried binding ItemsControl's Width to the ScrollViewer's Width but it didn't work either (<code>Width="{Binding ElementName=MyScrollerName, Path=Width}"</code>).</p>
  
  <p>What am I doing wrong?</p>