title: ListBox in TabControl scrolling issue
body: <p>I have an issue with WPF ListBox in TabControl. ListBox resets it's scrollbar position to 0 when I change tabs. Here is repro code:</p>
  
  <pre><code>&lt;TabControl x:Name="_tabs"&gt;
      &lt;TabItem Header="1"&gt;
          &lt;ListBox ItemsSource="{Binding}" ScrollViewer.VerticalScrollBarVisibility="Auto"/&gt;
      &lt;/TabItem&gt;
      &lt;TabItem Header="2"&gt;
          &lt;ListBox ItemsSource="{Binding}" ScrollViewer.VerticalScrollBarVisibility="Auto"/&gt;
      &lt;/TabItem&gt;
  &lt;/TabControl&gt;
  
  _tabs.DataContext = Enumerable.Range(1, 300).ToArray();
  </code></pre>
  
  <p>When the window opens I open the second tab, scroll list somewhere to the middle, return to the first tab and then open the second again. For some reason the list is scrolled to the top.  </p>
  
  <p>Why this happens? Have I made some stupid mistake?</p>