### Preflight Checklist

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

It would appear that `app.focus()` stopped working in Electron 6, and remains broken in Electron 8.

* **Electron Version:**
  * 8.0.3
* **Operating System:**
  * macOS
* **Last Known Working Electron version:**
  * 5.0.13

### Expected Behavior
`app.focus()` should bring the application to the foreground.

### Actual Behavior
`app.focus()` does nothing.

### To Reproduce

Fiddle: https://gist.github.com/a772265b312329e3f3bc1feb7b6aff7d

1) Start this fiddle.
2) As soon as the window pops up, select another application so that Electron is in the background.
3) Within 5 seconds, the app will attempt to focus itself to no avail.

shell/browser/browser_linux.cc
: public base::ScopedAllowBaseSyncPrimitivesForTesting {};
class GetXdgAppOutputScopedAllowBlocking
    : public base::ScopedAllowBlockingForTesting {};
bool LaunchXdgUtility(const std::vector<std::string>& argv, int* exit_code) {
  *exit_code = EXIT_FAILURE;
  int devnull = open("/dev/null", O_RDONLY);
  if (devnull < 0)
    return false;
  base::LaunchOptions options;
  options.fds_to_remap.emplace_back(devnull, STDIN_FILENO);
  base::Process process = base::LaunchProcess(argv, options);
  close(devnull);
  if (!process.IsValid())
    return false;
  LaunchXdgUtilityScopedAllowBaseSyncPrimitives allow_base_sync_primitives;
  return process.WaitForExit(exit_code);
}
base::Optional<std::string> GetXdgAppOutput(