class CallbackServerStreamingHandler;
template <StatusCode code>
class ErrorMethodHandler;
+class ExternalConnectionAcceptorImpl;
template <class R>
class DeserializeFuncType;
class GrpcByteBufferPeer;
friend class ProtoBufferReader;
friend class ProtoBufferWriter;
friend class internal::GrpcByteBufferPeer;
+ friend class internal::ExternalConnectionAcceptorImpl;
grpc_byte_buffer* buffer_;