* 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.h
std::vector<std::string>* additional_schemes) override;
  void SiteInstanceDeleting(content::SiteInstance* site_instance) override;
  std::unique_ptr<net::ClientCertStore> CreateClientCertStore(
      content::ResourceContext* resource_context) override;
  std::unique_ptr<device::LocationProvider> OverrideSystemLocationProvider()
      override;
  network::mojom::NetworkContextPtr CreateNetworkContext(
      content::BrowserContext* browser_context,
      bool in_memory,
      const base::FilePath& relative_partition_path) override;
  void RegisterOutOfProcessServices(OutOfProcessServiceMap* services) override;
  std::unique_ptr<base::Value> GetServiceManifestOverlay(
      base::StringPiece name) override;
  net::NetLog* GetNetLog() override;
  content::MediaObserver* GetMediaObserver() override;
  content::DevToolsManagerDelegate* GetDevToolsManagerDelegate() override;
  content::PlatformNotificationService* GetPlatformNotificationService()
      override;
  content::BrowserMainParts* CreateBrowserMainParts(
      const content::MainFunctionParams&) override;
  base::FilePath GetDefaultDownloadDirectory() override;
  scoped_refptr<network::SharedURLLoaderFactory>
  GetSystemSharedURLLoaderFactory() override;
  void OnNetworkServiceCreated(
      network::mojom::NetworkService* network_service) override;
  bool ShouldBypassCORB(int render_process_id) const override;
  
  void RenderProcessHostDestroyed(content::RenderProcessHost* host) override;
  void RenderProcessReady(content::RenderProcessHost* host) override;
  void RenderProcessExited(