* 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
content::ResourceContext* resource_context) {
#if defined(USE_NSS_CERTS)
  return std::make_unique<net::ClientCertStoreNSS>(
      net::ClientCertStoreNSS::PasswordDelegateFactory());
#elif defined(OS_WIN)
  return std::make_unique<net::ClientCertStoreWin>();
#elif defined(OS_MACOSX)
  return std::make_unique<net::ClientCertStoreMac>();
#elif defined(USE_OPENSSL)
  return std::unique_ptr<net::ClientCertStore>();
#endif
}
std::unique_ptr<device::LocationProvider>
AtomBrowserClient::OverrideSystemLocationProvider() {
#if BUILDFLAG(OVERRIDE_LOCATION_PROVIDER)
  return std::make_unique<FakeLocationProvider>();
#else
  return nullptr;
#endif
}
network::mojom::NetworkContextPtr AtomBrowserClient::CreateNetworkContext(
    content::BrowserContext* browser_context,
    bool ,
    const base::FilePath& ) {
  if (!browser_context)
    return nullptr;
  return static_cast<AtomBrowserContext*>(browser_context)->GetNetworkContext();
}
void AtomBrowserClient::RegisterOutOfProcessServices(