[MacOS] Tabbed Page Top Offset Fix (#1042)

* Tabbed Page Top Offset Fix

* Fixed Tabs

Xamarin.Forms.Platform.MacOS/Renderers/TabbedPageRenderer.cs

@@ -101,8 +101,13 @@ namespace Xamarin.Forms.Platform.MacOS
 			if (!Element.Bounds.IsEmpty)
 				View.Frame = new System.Drawing.RectangleF((float)Element.X, (float)Element.Y, (float)Element.Width, (float)Element.Height);
 
+			var topOffset = TabHolderHeight;
+			var tabStyle = Tabbed.OnThisPlatform().GetTabsStyle();
+			if (tabStyle == TabsStyle.Hidden || tabStyle == TabsStyle.OnNavigation)
+				topOffset = 0;
+
 			var frame = View.Frame;
-			Page.ContainerArea = new Rectangle(0, 0, frame.Width, frame.Height - TabHolderHeight);
+			Page.ContainerArea = new Rectangle(0, 0, frame.Width, frame.Height - topOffset);
 
 			if (!_queuedSize.IsZero)
 			{