* 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
protected:
  void RenderProcessWillLaunch(
      content::RenderProcessHost* host,
      service_manager::mojom::ServiceRequest* service_request) override;
  content::SpeechRecognitionManagerDelegate*
  CreateSpeechRecognitionManagerDelegate() override;
  content::TtsControllerDelegate* GetTtsControllerDelegate() override;
  void OverrideWebkitPrefs(content::RenderViewHost* render_view_host,
                           content::WebPreferences* prefs) override;
  SiteInstanceForNavigationType ShouldOverrideSiteInstanceForNavigation(
      content::RenderFrameHost* current_rfh,
      content::RenderFrameHost* speculative_rfh,
      content::BrowserContext* browser_context,
      const GURL& url,
      bool has_request_started,
      content::SiteInstance** affinity_site_instance) const override;
  void RegisterPendingSiteInstance(
      content::RenderFrameHost* render_frame_host,
      content::SiteInstance* pending_site_instance) override;
  void AppendExtraCommandLineSwitches(base::CommandLine* command_line,
                                      int child_process_id) override;
  void DidCreatePpapiPlugin(content::BrowserPpapiHost* browser_host) override;
  std::string GetGeolocationApiKey() override;
  content::QuotaPermissionContext* CreateQuotaPermissionContext() override;
  content::GeneratedCodeCacheSettings GetGeneratedCodeCacheSettings(
      content::BrowserContext* context) override;
  void AllowCertificateError(
      content::WebContents* web_contents,
      int cert_error,
      const net::SSLInfo& ssl_info,