* 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
int process_id,
    AtomBrowserClient::ProcessPreferences prefs) {
  base::AutoLock auto_lock(process_preferences_lock_);
  process_preferences_[process_id] = prefs;
}
void AtomBrowserClient::RemoveProcessPreferences(int process_id) {
  base::AutoLock auto_lock(process_preferences_lock_);
  process_preferences_.erase(process_id);
}
bool AtomBrowserClient::IsProcessObserved(int process_id) const {
  base::AutoLock auto_lock(process_preferences_lock_);
  return process_preferences_.find(process_id) != process_preferences_.end();
}
bool AtomBrowserClient::IsRendererSandboxed(int process_id) const {