Grid.IsSharedSizeScope="True" is not working inside ComboBox Popup

[AlexeiScherbakov]

Describe the bug

I redefined Style for creating custom ComboBox with popup with 2 columns, but Grid.IsSharedSizeScope="True" is not working

<Popup Name="PART_Popup"
       WindowManagerAddShadowHint="False"
       IsOpen="{TemplateBinding IsDropDownOpen, Mode=TwoWay}"
       MinWidth="{Binding Bounds.Width, RelativeSource={RelativeSource TemplatedParent}}"
       MaxHeight="{TemplateBinding MaxDropDownHeight}"
       PlacementTarget="Background"
       IsLightDismissEnabled="True"
       InheritsTransform="True">
  <Border x:Name="PopupBorder"
          Background="{DynamicResource ComboBoxDropDownBackground}"
          BorderBrush="{DynamicResource ComboBoxDropDownBorderBrush}"
          BorderThickness="{DynamicResource ComboBoxDropdownBorderThickness}"
          Padding="{DynamicResource ComboBoxDropdownBorderPadding}"
          HorizontalAlignment="Stretch"
          CornerRadius="{DynamicResource OverlayCornerRadius}"
          >
    <DockPanel Grid.IsSharedSizeScope="True">
      <TextBlock Text="This combobox is modified" DockPanel.Dock="Top"/>
      <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                    VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
                    IsDeferredScrollingEnabled="{TemplateBinding (ScrollViewer.IsDeferredScrollingEnabled)}"
                    HorizontalContentAlignment="Stretch">
        <ItemsPresenter Name="PART_ItemsPresenter"
                        Margin="{DynamicResource ComboBoxDropdownContentMargin}"
                        ItemsPanel="{TemplateBinding ItemsPanel}"
                        />
      </ScrollViewer>
    </DockPanel>
  </Border>
</Popup>

Same layout without popup is working

<DockPanel Grid.IsSharedSizeScope="True">
  <Grid DockPanel.Dock="Top">
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width="16"/>
      <ColumnDefinition Width="Auto" SharedSizeGroup="NameGroup"/>
      <ColumnDefinition Width="16"/>
      <ColumnDefinition Width="Auto" SharedSizeGroup="CountGroup"/>
    </Grid.ColumnDefinitions>
    <TextBlock Grid.Column="1" Text="Name"  Background="Red"/>
    <TextBlock Grid.Column="3" Text="Count" Background="Blue"/>
  </Grid>
  <ScrollViewer Margin="0">
    <ItemsControl ItemsSource="{Binding Path=Items}">
      <ItemsControl.ItemTemplate>
        <DataTemplate x:DataType="vm:Item">
           <Grid>
            <Grid.ColumnDefinitions>
              <ColumnDefinition Width="16"/>
              <ColumnDefinition Width="Auto" SharedSizeGroup="NameGroup"/>
              <ColumnDefinition Width="16"/>
              <ColumnDefinition Width="Auto" SharedSizeGroup="CountGroup"/>
            </Grid.ColumnDefinitions>
            <TextBlock Grid.Column="1" Text="{Binding Path=Name}" Background="Red"/>
            <TextBlock Grid.Column="3" Text="{Binding Path=Count}" Background="Blue" />
          </Grid>
        </DataTemplate>
      </ItemsControl.ItemTemplate>
    </ItemsControl>
  </ScrollViewer>
</DockPanel>

To Reproduce

Sample is located here - https://github.com/AlexeiScherbakov/AvaloniaGridSharedScopeBug

Expected behavior

IsSharedSizeScope is working

Avalonia version

11.0.0, 11.0.4

OS

Windows

Additional context

No response