### 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

* **Electron Version:**
10.0.0-nightly.20200220
* **Operating System:**
macOS 10.15.1
* **Last Known Working Electron version:**
I don't know (judging by implementation it never worked)

### Expected Behavior:
Call to BrowserWindow.webContents.focus focuses proper window

### Actual Behavior:
Call  to BrowserWindow.webContents.focus does nothing

### To Reproduce:

Run following simple app:
```
const { app, BrowserWindow } = require('electron')

function createWindow () {
  let win1 = new BrowserWindow({ x:100, y: 300, width: 300, height: 200 })
  win1.on('closed', () => {
    win1 = null
  })
  win1.loadURL('https://github.com')

  let win2 = new BrowserWindow({ x:300, y: 300, width: 300, height: 200 })
  win2.on('closed', () => {
    win1 = null
  })
  win2.loadURL('http://www.example.com')

  setTimeout(() => {
    win1.webContents.focus();
  }, 3000);
}

app.on('ready', createWindow)
```

It works as expected on Windows: it creates two windows and after three seconds it focuses the first one. On mac it doesn't work and call to `webContents.focus` doesn't change the focus (it stays on the second window).
shell/browser/api/electron_api_web_contents.cc
settings.SetIntKey(printing::kSettingDuplexMode, duplex_mode);
  // We've already done necessary parameter sanitization at the
  // JS level, so we can simply pass this through.
  base::Value media_size(base::Value::Type::DICTIONARY);
  if (options.Get("mediaSize", &media_size))
    settings.SetKey(printing::kSettingMediaSize, std::move(media_size));
  // Set custom dots per inch (dpi)
  gin_helper::Dictionary dpi_settings;
  int dpi = 72;
  if (options.Get("dpi", &dpi_settings)) {
    int horizontal = 72;
    dpi_settings.Get("horizontal", &horizontal);
    settings.SetIntKey(printing::kSettingDpiHorizontal, horizontal);
    int vertical = 72;
    dpi_settings.Get("vertical", &vertical);
    settings.SetIntKey(printing::kSettingDpiVertical, vertical);
  } else {
    settings.SetIntKey(printing::kSettingDpiHorizontal, dpi);
    settings.SetIntKey(printing::kSettingDpiVertical, dpi);
  }
  base::PostTaskAndReplyWithResult(
      FROM_HERE,
      {base::ThreadPool(), base::MayBlock(), base::TaskPriority::USER_BLOCKING},
      base::BindOnce(&GetDefaultPrinterAsync),
      base::BindOnce(&Ws::OnGetDefaultPrinter,
                     weak_factory_.GetWeakPtr(), std::move(settings),
                     std::move(callback), device_name, silent));
}
std::vector<printing::PrinterBasicInfo> Ws::GetPrinterList() {
  std::vector<printing::PrinterBasicInfo> printers;