Add ScreenBounds method to IRender interface.

This method is expected to return Rectangles that cover
the region where Renderables returned by Render may exist.

OpenRA.Mods.Common/Traits/Render/RenderSprites.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Graphics;
 using OpenRA.Mods.Common.Graphics;
@@ -181,6 +182,13 @@ namespace OpenRA.Mods.Common.Traits.Render
 			}
 		}
 
+		public virtual IEnumerable<Rectangle> ScreenBounds(Actor self, WorldRenderer wr)
+		{
+			foreach (var a in anims)
+				if (a.IsVisible)
+					yield return a.Animation.ScreenBounds(self, wr, info.Scale);
+		}
+
 		void ITick.Tick(Actor self)
 		{
 			Tick(self);