Extracted ICodedInputStream interface
diff --git a/src/ProtocolBuffers/GeneratedBuilder.cs b/src/ProtocolBuffers/GeneratedBuilder.cs
index 699320a..4d4be21 100644
--- a/src/ProtocolBuffers/GeneratedBuilder.cs
+++ b/src/ProtocolBuffers/GeneratedBuilder.cs
@@ -115,7 +115,7 @@
         /// </summary>

         /// <returns>true unless the tag is an end-group tag</returns>

         [CLSCompliant(false)]

-        protected virtual bool ParseUnknownField(CodedInputStream input, UnknownFieldSet.Builder unknownFields,

+        protected virtual bool ParseUnknownField(ICodedInputStream input, UnknownFieldSet.Builder unknownFields,

                                                  ExtensionRegistry extensionRegistry, uint tag, string fieldName)

         {

             return unknownFields.MergeFieldFrom(tag, input);