title: Border contents escapes even when using ClipToBounds & CornerRadius
body: <p>I have a custom control that sits inside a border, the border has a <code>CornerRadius</code> and an inner shadow that should create a nice look. Inside that border is a custom Control but that control seems to ignore the border radius and makes it look square when the control is placed underneath a corner.  How can I fix this?</p>
  
  <pre><code>&lt;Border Background="#ccc" BorderBrush="Transparent" BorderThickness="1" ClipToBounds="True" CornerRadius="5"&gt;
      &lt;Border Background="Transparent" BorderBrush="Gray"  ClipToBounds="True" CornerRadius="5" BorderThickness="1" Margin="0"&gt;
          &lt;Grid&gt;
              &lt;Toolkit:CanvasControl HorizontalAlignment="Stretch" VerticalAlignment="Stretch"&gt; 
              &lt;!-- more contents here --&gt;
              &lt;/Toolkit:CanvasControl&gt;
          &lt;/Grid&gt;
      &lt;/Border&gt;
  &lt;/Border&gt;
  </code></pre>
  
  <p>The <code>CanvasControl</code> is defined as so</p>
  
  <pre><code>public class CanvasControl : Panel
  {
  }
  </code></pre>