electron code head commit:  2fb9085e5b9b28b7adf0ab7de720c87461b6689d
os: win10 64bit
visual studio 2019 preview

after build electron , I run 
```
electron.exe electron/spec
```
and the program crash, i use vs2019 debug it, see the picture, 
![捕获](https://user-images.githubusercontent.com/43543863/54986357-7331d580-4fed-11e9-9419-0775d533d3fe.PNG)

device_names is empty, and the code does not check it
atom/browser/api/atom_api_desktop_capturer.cc
if (using_directx_capturer_) {
      std::vector<std::string> device_names;
      
      
      webrtc::DxgiDuplicatorController::Instance()->GetDeviceNames(
          &device_names);
      int device_name_index = 0;
      for (auto& source : screen_sources) {
        const auto& device_name = device_names[device_name_index++];
        std::wstring wide_device_name;
        base::UTF8ToWide(device_name.c_str(), device_name.size(),
                         &wide_device_name);
        const int64_t device_id =
            display::win::DisplayInfo::DeviceIdFromDeviceName(
                wide_device_name.c_str());
        source.display_id = base::NumberToString(device_id);
      }
    }
#elif defined(OS_MACOSX)
    
    for (auto& source : screen_sources) {
      source.display_id = base::NumberToString(source.media_list_source.id.id);
    }
#endif