title: Transforms on WriteableBitmap
body: <p>I'm writing app in WP7 mango and try to transform image loaded from binded to WriteableBitmap in XAML for example like this:</p>
  
  <pre><code>&lt;Grid&gt;
      &lt;ScrollViewer&gt;
          &lt;Image Source="{Binding SourceImage}"&gt;
              &lt;Image.RenderTransform&gt;
                  &lt;RotateTransform Angle="{Binding RotateAngle}"/&gt;
              &lt;/Image.RenderTransform&gt;
          &lt;/Image&gt;
      &lt;/ScrollViewer&gt;
  &lt;/Grid&gt; 
  </code></pre>
  
  <p>I bind Angle with my property Angle in my ViewModel, i change from slider this value but image doesn't rotate. Raising property changed is working correct. 
  When i do it with image loaded from contets file, static image, it works.</p>