Refactoring the ICoded interfaces (again) removing the use of some generic methods.
diff --git a/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs b/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
index ec1670f..e875b6f 100644
--- a/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
+++ b/src/ProtocolBuffers.Test/TestProtos/UnitTestMessageSetProtoFile.cs
@@ -1385,7 +1385,7 @@
       int size = SerializedSize;

       string[] field_names = _rawMessageSetFieldNames;

       if (item_.Count > 0) {

-        output.WriteArray(pbd::FieldType.Group, 1, field_names[0], item_);

+        output.WriteGroupArray(1, field_names[0], item_);

       }

       UnknownFields.WriteTo(output);

     }