Add write buffer hint to C++ server handlers so that writes actually go

out when expected.

src/cpp/server/async_server_context.cc

@@ -54,7 +54,7 @@ AsyncServerContext::~AsyncServerContext() { grpc_call_destroy(call_); }
 
 void AsyncServerContext::Accept(grpc_completion_queue *cq) {
   GPR_ASSERT(grpc_call_server_accept(call_, cq, this) == GRPC_CALL_OK);
-  GPR_ASSERT(grpc_call_server_end_initial_metadata(call_, 0) == GRPC_CALL_OK);
+  GPR_ASSERT(grpc_call_server_end_initial_metadata(call_, GRPC_WRITE_BUFFER_HINT) == GRPC_CALL_OK);
 }
 
 bool AsyncServerContext::StartRead(google::protobuf::Message *request) {

src/cpp/server/server_rpc_handler.cc

@@ -77,7 +77,7 @@ void ServerRpcHandler::StartRpc() {
 
     if (status.IsOk()) {
       // Send the response if we get an ok status.
-      async_server_context_->StartWrite(*response, 0);
+      async_server_context_->StartWrite(*response, GRPC_WRITE_BUFFER_HINT);
       type = WaitForNextEvent();
       if (type != CompletionQueue::SERVER_WRITE_OK) {
         status = Status(StatusCode::INTERNAL, "Error writing response.");