Fix CA1852

OpenRA.Mods.Common/FileFormats/Blast.cs

@@ -200,7 +200,7 @@ namespace OpenRA.Mods.Common.FileFormats
 		}
 	}
 
-	class BitReader
+	sealed class BitReader
 	{
 		readonly Stream stream;
 		byte bitBuffer = 0;
@@ -242,7 +242,7 @@ namespace OpenRA.Mods.Common.FileFormats
 	 * codes.  Those tables are the number of codes of each length, and the symbols
 	 * sorted by length, retaining their original order within each length.
 	 */
-	class Huffman
+	sealed class Huffman
 	{
 		public short[] Count; // number of symbols of each length
 		public short[] Symbol; // canonically ordered symbols

OpenRA.Mods.Common/FileFormats/InstallShieldCABCompression.cs

@@ -242,7 +242,7 @@ namespace OpenRA.Mods.Common.FileFormats
 			}
 		}
 
-		class CabExtracter
+		sealed class CabExtracter
 		{
 			readonly FileDescriptor file;
 			readonly Dictionary<int, Stream> volumes;

OpenRA.Mods.Common/FileFormats/MSCabCompression.cs

@@ -20,7 +20,7 @@ namespace OpenRA.Mods.Common.FileFormats
 {
 	public sealed class MSCabCompression
 	{
-		class CabFolder
+		sealed class CabFolder
 		{
 			public readonly uint BlockOffset;
 			public readonly ushort BlockCount;
@@ -34,7 +34,7 @@ namespace OpenRA.Mods.Common.FileFormats
 			}
 		}
 
-		class CabFile
+		sealed class CabFile
 		{
 			public readonly string FileName;
 			public readonly uint DecompressedLength;