title: WPF - width issue with IsSharedSizeScope "true" and three columns
body: <p>Simple code:</p>
  
  <pre><code>&lt;ItemsControl Grid.IsSharedSizeScope="True" &gt;
      &lt;ItemsControl.ItemTemplate&gt;
          &lt;DataTemplate&gt;
              &lt;Grid&gt;
                  &lt;Grid.ColumnDefinitions&gt;
                      &lt;ColumnDefinition SharedSizeGroup="firstColumn" Width="Auto"/&gt;
                      &lt;ColumnDefinition SharedSizeGroup="splitterColumn" Width="Auto"/&gt;
                      &lt;ColumnDefinition SharedSizeGroup="lastColumn" Width="*"/&gt;
                  &lt;/Grid.ColumnDefinitions&gt;
                  &lt;TextBlock Text="{Binding Path=Key}"/&gt;
                  &lt;GridSplitter Width="5" Grid.Column="1" /&gt;
                  &lt;TextBlock Text="{Binding Path=Value}" Grid.Column="2"/&gt;
              &lt;/Grid&gt;
          &lt;/DataTemplate&gt;
      &lt;/ItemsControl.ItemTemplate&gt;
  &lt;/ItemsControl&gt;
  </code></pre>
  
  <p>Problem is occured with <code>lastColumn</code>, <code>width</code> of it is not 100%. I try to set <code>HorizontalAlignment="Stretch"</code> for the all grids but it didn't help.</p>
  
  <p>Width of <code>lastColumn</code> must be 100%. How to resolve this issue?</p>