message: Initialize only CPU devices in optimize_dataset_op
diff: @@ -103,7 +103,11 @@ Status OptimizeGraph(const GraphDef& graph_def_arg, GraphDef* output_graph_def,
  // Instantiate all variables for function library runtime creation.
  std::vector<std::unique_ptr<Device>> devices;
  - TF_RETURN_IF_ERROR(DeviceFactory::AddDevices(
  + // Only CPU device is used so instead of calling DeviceFactory::AddDevices()
  + // with dummy session config, which will conflict with user defined options and
  + // create unwanted devices, call cpu_factory->CreateDevices() to get CPU only devices.
  + DeviceFactory* cpu_factory = DeviceFactory::GetFactory("CPU");
  + TF_RETURN_IF_ERROR(cpu_factory->CreateDevices(
  options, "/job:localhost/replica:0/task:0", &devices));
  Device* cpu_device = devices[0].get();
  std::unique_ptr<DeviceMgr> dvc_mgr(new DeviceMgr(std::move(devices)));
  