* 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
std::vector<std::string>* additional_schemes) {
  auto schemes_list = api::GetStandardSchemes();
  if (!schemes_list.empty())
    additional_schemes->insert(additional_schemes->end(), schemes_list.begin(),
                               schemes_list.end());
  additional_schemes->push_back(content::kChromeDevToolsScheme);
}
void AtomBrowserClient::GetAdditionalWebUISchemes(
    std::vector<std::string>* additional_schemes) {
  additional_schemes->push_back(content::kChromeDevToolsScheme);
}
void AtomBrowserClient::SiteInstanceDeleting(
    content::SiteInstance* site_instance) {
  
  
  for (auto iter = site_per_affinities_.begin();
       iter != site_per_affinities_.end(); ++iter) {
    if (iter->second == site_instance) {
      site_per_affinities_.erase(iter);
      break;
    }
  }
}
std::unique_ptr<net::ClientCertStore> AtomBrowserClient::CreateClientCertStore(