[iOS/Android] Move Map camera to correct region on layout change (#548)

* Move to region on layout change

* remove visibility check

Xamarin.Forms.Maps.Android/MapRenderer.cs

@@ -186,6 +186,7 @@ namespace Xamarin.Forms.Maps.Android
 			else if (changed)
 			{
 				UpdateVisibleRegion(NativeMap.CameraPosition.Target);
+				MoveToRegion(Element.LastMoveToRegion, false);
 			}
 		}
 

Xamarin.Forms.Maps.iOS/MapRenderer.cs

@@ -190,7 +190,7 @@ namespace Xamarin.Forms.Maps.iOS
 				UpdateHasScrollEnabled();
 			else if (e.PropertyName == Map.HasZoomEnabledProperty.PropertyName)
 				UpdateHasZoomEnabled();
-			else if (e.PropertyName == VisualElement.IsVisibleProperty.PropertyName && ((Map)Element).LastMoveToRegion != null)
+			else if (e.PropertyName == VisualElement.HeightProperty.PropertyName && ((Map)Element).LastMoveToRegion != null)
 				_shouldUpdateRegion = true;
 		}