* 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::RenderProcessHost* host) {
  int process_id = host->GetID();
  pending_processes_.erase(process_id);
  RemoveProcessPreferences(process_id);
}
void AtomBrowserClient::RenderProcessReady(content::RenderProcessHost* host) {
  render_process_host_pids_[host->GetID()] =
      base::GetProcId(host->GetProcess().Handle());
  if (delegate_) {
    static_cast<api::App*>(delegate_)->RenderProcessReady(host);
  }
}
void AtomBrowserClient::RenderProcessExited(
    content::RenderProcessHost* host,
    const content::ChildProcessTerminationInfo& info) {
  auto host_pid = render_process_host_pids_.find(host->GetID());
  if (host_pid != render_process_host_pids_.end()) {
    if (delegate_) {
      static_cast<api::App*>(delegate_)->RenderProcessDisconnected(
          host_pid->second);
    }
    render_process_host_pids_.erase(host_pid);
  }
}
void OnOpenExternal(const GURL& escaped_url, bool allowed) {