Ensure templated parent control theme is applied.

src/Avalonia.Base/Layout/Layoutable.cs

@@ -795,6 +795,12 @@ namespace Avalonia.Layout
             InvalidateMeasure();
         }
 
+        internal override void OnTemplatedParentControlThemeChanged()
+        {
+            base.OnTemplatedParentControlThemeChanged();
+            InvalidateMeasure();
+        }
+
         /// <summary>
         /// Called when the layout manager raises a LayoutUpdated event.
         /// </summary>

src/Avalonia.Base/StyledElement.cs

@@ -390,7 +390,7 @@ namespace Avalonia
         /// </returns>
         public bool ApplyStyling()
         {
-            if (_initCount == 0 && (!_stylesApplied || !_themeApplied))
+            if (_initCount == 0 && (!_stylesApplied || !_themeApplied || !_templatedParentThemeApplied))
             {
                 GetValueStore().BeginStyling();