### 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
v8::Isolate* isolate,
    std::unique_ptr<content::Ws> owned_ontents,
    gin::Handle<api::Session> session,
    const gin_helper::Dictionary& options) {
  Observe(owned_ontents.get());
  
  
  
  InitWithWs(owned_ontents.release(), session->browser_context(),
                      IsGuest());
  managed_ontents()->GetView()->SetDelegate(this);
  auto* prefs = ontents()->GetMutableRendererPrefs();
  prefs->accept_languages = g_browser_process->GetApplicationLocale();
#if defined(OS_LINUX) || defined(OS_WIN)
  
  static const base::NoDestructor<gfx::FontRenderParams> params(
      gfx::GetFontRenderParams(gfx::FontRenderParamsQuery(), nullptr));
  prefs->should_antialias_text = params->antialiasing;
  prefs->use_subpixel_positioning = params->subpixel_positioning;
  prefs->hinting = params->hinting;
  prefs->use_autohinter = params->autohinter;
  prefs->use_bitmaps = params->use_bitmaps;
  prefs->subpixel_rendering = params->subpixel_rendering;
#endif
  
  if (auto interval = GetCursorBlinkInterval())
    prefs->caret_blink_interval = *interval;
  
  new WsPreferences(ontents(), options);
  WsPermissionHelper::CreateForWs(ontents());