Directly use the ZeroCopyInputStream for grpc::GenericDeserialize.

There is no need to use CodedInputStream, wrapping a
ZeroCopyInputStream.

Suggested by: Gerben Stavenga

include/grpcpp/impl/codegen/proto_utils.h

@@ -83,14 +83,9 @@ Status GenericDeserialize(ByteBuffer* buffer,
     if (!reader.status().ok()) {
       return reader.status();
     }
-    ::grpc::protobuf::io::CodedInputStream decoder(&reader);
+    if (!msg->ParseFromZeroCopyStream(&reader)) {
-    decoder.SetTotalBytesLimit(INT_MAX, INT_MAX);
-    if (!msg->ParseFromCodedStream(&decoder)) {
       result = Status(StatusCode::INTERNAL, msg->InitializationErrorString());
     }
-    if (!decoder.ConsumedEntireMessage()) {
-      result = Status(StatusCode::INTERNAL, "Did not read entire message");
-    }
   }
   buffer->Clear();
   return result;