* 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
content::RenderProcessHost* host,
    service_manager::mojom::ServiceRequest* service_request) {
  
  int process_id = host->GetID();
  if (IsProcessObserved(process_id))
    return;
#if BUILDFLAG(ENABLE_PRINTING)
  host->AddFilter(new printing::PrintingMessageFilter(
      process_id, host->GetBrowserContext()));
#endif
#if BUILDFLAG(ENABLE_TTS)
  host->AddFilter(new TtsMessageFilter(host->GetBrowserContext()));
#endif
  ProcessPreferences prefs;
  auto* web_preferences =
      WebContentsPreferences::From(GetWebContentsFromProcessID(process_id));
  if (web_preferences) {
    prefs.sandbox = web_preferences->IsEnabled(options::kSandbox);
    prefs.native_window_open =
        web_preferences->IsEnabled(options::kNativeWindowOpen);
    prefs.disable_popups = web_preferences->IsEnabled("disablePopups");
    prefs.web_security = web_preferences->IsEnabled(options::kWebSecurity,
                                                    true );
  }
  AddProcessPreferences(host->GetID(), prefs);
  
  host->AddObserver(this);
}
content::SpeechRecognitionManagerDelegate*