* 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
AtomBrowserClient::ShouldOverrideSiteInstanceForNavigation(
    content::RenderFrameHost* current_rfh,
    content::RenderFrameHost* speculative_rfh,
    content::BrowserContext* browser_context,
    const GURL& url,
    bool has_response_started,
    content::SiteInstance** affinity_site_instance) const {
  if (g_suppress_renderer_process_restart) {
    g_suppress_renderer_process_restart = false;
    return SiteInstanceForNavigationType::ASK_CHROMIUM;
  }
  
  content::SiteInstance* site_instance_from_affinity =
      GetSiteInstanceFromAffinity(browser_context, url, current_rfh);
  if (site_instance_from_affinity) {
    *affinity_site_instance = site_instance_from_affinity;
    return SiteInstanceForNavigationType::FORCE_AFFINITY;
  }