Changes ISpriteSource.Frames to be of type IReadOnlyList<ISpriteFrame>.

- Updated implementations to return a ReadOnlyList around an array (to reduce wasted memory from exposing lists or lazy enumerators around lists).
- Protect non-public ISpriteFrame classes by making them inner classes to prevent casting.
- Added an AsReadOnly extension method for lists.

OpenRA.Game/FileFormats/TmpTSReader.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2013 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2014 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. For more information,
@@ -39,7 +39,7 @@ namespace OpenRA.FileFormats
 				for (var j = 0; j < width; j++)
 					Data[start + j] = s.ReadUInt8();
 
-				width += (i < size.Height / 2 - 1? 1 : -1) * 4;
+				width += (i < size.Height / 2 - 1 ? 1 : -1) * 4;
 			}
 
 			// Ignore Z-data for now
@@ -49,8 +49,7 @@ namespace OpenRA.FileFormats
 
 	public class TmpTSReader : ISpriteSource
 	{
-		readonly List<ISpriteFrame> tiles = new List<ISpriteFrame>();
-		public IEnumerable<ISpriteFrame> Frames { get { return tiles; } }
+		public IReadOnlyList<ISpriteFrame> Frames { get; private set; }
 		public bool CacheWhenLoadingTileset { get { return false; } }
 
 		public TmpTSReader(Stream s)
@@ -64,11 +63,14 @@ namespace OpenRA.FileFormats
 			for (var i = 0; i < offsets.Length; i++)
 				offsets[i] = s.ReadUInt32();
 
+			var tiles = new List<TmpTSTile>();
 			for (var i = 0; i < offsets.Length; i++)
 			{
 				s.Position = offsets[i];
 				tiles.Add(new TmpTSTile(s, size));
 			}
+
+			Frames = tiles.ToArray().AsReadOnly();
 		}
 	}
 }