title: GridSplitter not resizing content in grid
body: <p>I have a <code>Grid</code> with 2 rows and 4 columns.</p>
  
  <pre><code>&lt;Grid.ColumnDefinitions&gt;
      &lt;ColumnDefinition Width="Auto" MinWidth="144"/&gt;
      &lt;ColumnDefinition Width="Auto" MinWidth="136"/&gt;
      &lt;ColumnDefinition Width="*"/&gt;
      &lt;ColumnDefinition Width="Auto" MinWidth="290"/&gt;
  </code></pre>
  
  <p></p>
  
  <p>
         
         
         
     </p>
  
  <p>3rd column has a <code>GridSplitter</code>:</p>
  
  <pre><code>&lt;GridSplitter Grid.Column ="3" Background="Gray"  ResizeDirection="Columns" 
                Grid.RowSpan="3"
                HorizontalAlignment="Stretch" 
                VerticalAlignment="Stretch" 
                Margin="7,-2,278,1"/&gt;
  </code></pre>
  
  <p>After adding the splitter, it doesn't stretch to left or right. Is there some other implementation I need to do to to split and expand content in the grid?</p>