* 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
if (!ShouldForceNewSiteInstance(current_rfh, speculative_rfh, browser_context,
                                  url, has_response_started)) {
    return SiteInstanceForNavigationType::ASK_CHROMIUM;
  }
  
  
  
  
  
  
  
  
  
  
  if (has_response_started) {
    return SiteInstanceForNavigationType::FORCE_CURRENT;
  }
  return SiteInstanceForNavigationType::FORCE_CANDIDATE_OR_NEW;
}
void AtomBrowserClient::RegisterPendingSiteInstance(
    content::RenderFrameHost* rfh,
    content::SiteInstance* pending_site_instance) {
  
  ConsiderSiteInstanceForAffinity(rfh, pending_site_instance);
  
  auto* web_contents = content::WebContents::FromRenderFrameHost(rfh);
  auto* pending_process = pending_site_instance->GetProcess();
  pending_processes_[pending_process->GetID()] = web_contents;
}
void AtomBrowserClient::AppendExtraCommandLineSwitches(