Merge RGBA sprite rendering into SpriteRenderer.

Renderer.RgbaSpriteRenderer is kept as a thin
wrapper to maintain compatibility with consumer
code.

OpenRA.Game/Graphics/RgbaSpriteRenderer.cs

@@ -0,0 +1,52 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+
+namespace OpenRA.Graphics
+{
+	public class RgbaSpriteRenderer
+	{
+		readonly SpriteRenderer parent;
+
+		public RgbaSpriteRenderer(SpriteRenderer parent)
+		{
+			this.parent = parent;
+		}
+
+		public void DrawSprite(Sprite s, float3 location, float3 size)
+		{
+			if (s.Channel != TextureChannel.RGBA)
+				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");
+
+			parent.DrawSprite(s, location, 0, size);
+		}
+
+		public void DrawSprite(Sprite s, float3 location)
+		{
+			if (s.Channel != TextureChannel.RGBA)
+				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");
+
+			parent.DrawSprite(s, location, 0, s.Size);
+		}
+
+		public void DrawSprite(Sprite s, float3 a, float3 b, float3 c, float3 d)
+		{
+			if (s.Channel != TextureChannel.RGBA)
+				throw new InvalidOperationException("DrawRGBASprite requires a RGBA sprite.");
+
+			parent.DrawSprite(s, a, b, c, d);
+		}
+	}
+}