title: ScrollViewer Content size change then ScrollToOffset not working
body: <p>I am using a scrollviewer to display an Image within it.</p>
  
  <pre><code>&lt;ScrollViewer Name="scrollViewer1" Height="500" Width="500" HorizontalScrollBarVisibility="Auto" VerticalScrollBarVisibility="Auto" Padding="0" &gt;
      &lt;Image x:Name="img1" Width="100" Source="/MyApp;component/Images/Test.jpg" /&gt;
  &lt;/ScrollViewer&gt;
  </code></pre>
  
  <p>But when I re-size the image in code, and immediately use the <strong><em>scrollViewer.ScrollToHorizontalOffset()</em></strong> (to reposition the image) it does not work :</p>
  
  <pre><code>img1.Width = 1000;
  scrollViewer1.ScrollToHorizontalOffset(500);
  </code></pre>
  
  <p>I verified the <strong><em>ScrollableWidth</em></strong> property after the <code>img1.Width = 1000</code> indeed it is not updated yet. So I used the <strong><em>UpdateLayout()</em></strong> right after I resize the image, great now the <strong><em>ScrollableWidth</em></strong> is updated :</p>
  
  <pre><code>img1.Width = 1000;
  scrollViewer1.UpdateLayout();
  scrollViewer1.ScrollToHorizontalOffset(500);
  </code></pre>
  
  <p>but the <strong><em>ScrollToHorizontalOffset</em></strong> is still not working. If I do it afterwards, on another user button click it works though. :/</p>
  
  <p>Anyone has a clue?</p>