* 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
const GURL& request_url,
      content::ResourceType resource_type,
      bool strict_enforcement,
      bool expired_previous_decision,
      const base::Callback<void(content::CertificateRequestResultType)>&
          callback) override;
  void SelectClientCertificate(
      content::WebContents* web_contents,
      net::SSLCertRequestInfo* cert_request_info,
      net::ClientCertIdentityList client_certs,
      std::unique_ptr<content::ClientCertificateDelegate> delegate) override;
  void ResourceDispatcherHostCreated() override;
  bool CanCreateWindow(content::RenderFrameHost* opener,
                       const GURL& opener_url,
                       const GURL& opener_top_level_frame_url,
                       const GURL& source_origin,
                       content::mojom::WindowContainerType container_type,
                       const GURL& target_url,
                       const content::Referrer& referrer,
                       const std::string& frame_name,
                       WindowOpenDisposition disposition,
                       const blink::mojom::WindowFeatures& features,
                       const std::vector<std::string>& additional_features,
                       const scoped_refptr<network::ResourceRequestBody>& body,
                       bool user_gesture,
                       bool opener_suppressed,
                       bool* no_javascript_access) override;
  void GetAdditionalAllowedSchemesForFileSystem(
      std::vector<std::string>* additional_schemes) override;
  void GetAdditionalWebUISchemes(