### 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
const std::string& channel,
                              blink::CloneableMessage arguments,
                              MessageSyncCallback callback) {
  TRACE_EVENT1("electron", "Ws::MessageSync", "channel", channel);
  // ws.emit('-ipc-message-sync', new Event(sender, message), internal,
  // channel, arguments);
  EmitWithSender("-ipc-message-sync", bindings_.dispatch_context(),
                 std::move(callback), internal, channel, std::move(arguments));
}
void Ws::MessageTo(bool internal,
                            bool send_to_all,
                            int32_t ontents_id,
                            const std::string& channel,
                            blink::CloneableMessage arguments) {
  TRACE_EVENT1("electron", "Ws::MessageTo", "channel", channel);
  auto* ontents = gin_helper::TrackableObject<Ws>::FromWeakMapID(
      isolate(), ontents_id);
  if (ontents) {
    ontents->SendIPCMessageWithSender(internal, send_to_all, channel,
                                           std::move(arguments), ID());
  }
}
void Ws::MessageHost(const std::string& channel,