* Electron Version: 3.0.0-beta.2
* Operating System (Platform and Version): Current Windows 10, 64bit
* Last known working Electron version: 2.0.4

**Expected Behavior**
Full screen and all opened windows to be returned.

**Actual behavior**
Only full screen and a seemingly identical item are returned. Independent of the number of opened windows. 

**To Reproduce**
Call
```
desktopCapturer.getSources({
    types: ['window', 'screen'],
    thumbnailSize: {
          width: 250,
          height: 250
    }
}, function (err, sources) {

});
```
The `sources` contains only two items, the first one, which is the entire desktop screen is valid, the other one is not.


atom/browser/api/atom_api_desktop_capturer.cc
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::Int64ToString(device_id);
      }
    }
  }
#elif defined(OS_MACOSX)
  
  for (auto& source : sources) {
    if (source.media_list_source.id.type ==
        content::DesktopMediaID::TYPE_SCREEN) {
      source.display_id = base::Int64ToString(source.media_list_source.id.id);
    }
  }
#endif  
  
  
  
  content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
                                   base::Bind(EmitFinished, sources, cap));
}
}  
namespace atom {
namespace api {
DesktopCapturer::DesktopCapturer(v8::Isolate* isolate) {