* Output of `node_modules/.bin/electron --version`: v5.0.0-nightly.20190107
* Operating System (Platform and Version): macOS Mojave 10.14.2 (18C54)
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): never

**Expected Behavior**
Using navigator.mediaDevices.getDisplayMedia({ video: true }), a native screen picker should appear.

**Actual behavior**
The following error is thrown: NotAllowedError: Permission denied

**Screenshots**
Expected dialog
![image](https://user-images.githubusercontent.com/1120050/51625551-71736500-1f0b-11e9-9a95-1406cad95046.png)
atom/browser/atom_browser_client.cc
return MediaCaptureDevicesDispatcher::GetInstance();
}
content::DevToolsManagerDelegate*
AtomBrowserClient::GetDevToolsManagerDelegate() {
  return new DevToolsManagerDelegate;
}
NotificationPresenter* AtomBrowserClient::GetNotificationPresenter() {
  if (!notification_presenter_) {
    notification_presenter_.reset(NotificationPresenter::Create());
  }
  return notification_presenter_.get();
}
content::PlatformNotificationService*
AtomBrowserClient::GetPlatformNotificationService() {
  if (!notification_service_) {
    notification_service_.reset(new PlatformNotificationService(this));
  }
  return notification_service_.get();
}
base::FilePath AtomBrowserClient::GetDefaultDownloadDirectory() {
  
  base::FilePath path;
  if (base::PathService::Get(base::DIR_HOME, &path))
    path = path.Append(FILE_PATH_LITERAL("Downloads"));
  return path;
}
scoped_refptr<network::SharedURLLoaderFactory>