title: StackPanel inside of a ScrollView doesnt physically scroll correctly
body: <p>Consider the following XAML (a UserControl):</p>
  
  <pre><code>&lt;Grid x:Name="LayoutRoot" ScrollViewer.VerticalScrollBarVisibility="Disabled"&gt;
      &lt;Grid HorizontalAlignment="Right" Width="335.312" ScrollViewer.VerticalScrollBarVisibility="Disabled"&gt;
          &lt;ed:BlockArrow Fill="#FFF4F4F5" HorizontalAlignment="Left" Margin="0" Orientation="Left" Stroke="Black" Width="15" RenderTransformOrigin="5.6,-0.412" Height="12" VerticalAlignment="Center" MouseEnter="LeftArrow_MouseEnter" MouseLeave="LeftArrow_MouseLeave" MouseLeftButtonUp="LeftArrow_MouseLeftButtonUp"/&gt;
          &lt;ed:BlockArrow Fill="#FFF4F4F5" Stroke="Black" RenderTransformOrigin="5.6,-0.412" Height="12" VerticalAlignment="Center" MouseEnter="RightArrow_MouseEnter" MouseLeave="RightArrow_MouseLeave" HorizontalAlignment="Right" Width="15" MouseLeftButtonUp="RightArrow_MouseLeftButtonUp"/&gt;
          &lt;ScrollViewer x:Name="panelScrollViewer" Margin="15,0" VerticalScrollBarVisibility="Disabled" HorizontalScrollBarVisibility="Hidden"&gt;
              &lt;StackPanel x:Name="slidingStackPanel" Orientation="Horizontal" Height="125.882" Width="305.312" ScrollViewer.VerticalScrollBarVisibility="Disabled" CanHorizontallyScroll="True" ScrollViewer.CanContentScroll="False"/&gt;
          &lt;/ScrollViewer&gt;
      &lt;/Grid&gt;
  &lt;/Grid&gt;
  </code></pre>
  
  <p>I am looking to physically scroll this stackpanel. I dynamically add elements to the stackpanel, and this appears to work correctly. In another button's click function, the following code is executed:</p>
  
  <pre><code>panelScrollViewer.ScrollToHorizontalOffset(100);
  </code></pre>
  
  <p>The scrollview and the stackpanel's HorizonalOffset is still zero! Also, the stackpanel's ScrollOwner is null. Any ideas?</p>