message: Pre-allocate memory for vector where size is known.
diff: @@ -413,6 +413,7 @@ Status GrpcSession::Reset(const SessionOptions& options,
  /*rpc_options=*/nullptr, &master_channel));
  auto master = NewGrpcMaster(master_channel);
  ResetRequest req;
  + req.mutable_container()->Reserve(containers.size());
  for (const auto& c : containers) req.add_container(c);
  ResetResponse resp;
  CallOptions call_options;
  