Merge pull request #2717 from cwensley/curtis/wpf-scrollable-performance

WPF: Don't force layout when child preferred size changes

src/Eto.Wpf/Forms/Controls/ScrollableHandler.cs

@@ -221,7 +221,8 @@ public bool ExpandContentHeight
 		public override void OnChildPreferredSizeUpdated()
 		{
 			base.OnChildPreferredSizeUpdated();
-			UpdateScrollSizes();
+			if (ExpandContentWidth || ExpandContentHeight)
+				UpdateSizes();
 		}
 	}
 }