### 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
Emit("did-stop-loading");
}
bool Ws::EmitNavigationEvent(
    const std::string& event,
    content::NavigationHandle* navigation_handle) {
  bool is_main_frame = navigation_handle->IsInMainFrame();
  int frame_tree_node_id = navigation_handle->GetFrameTreeNodeId();
  content::FrameTreeNode* frame_tree_node =
      content::FrameTreeNode::GloballyFindByID(frame_tree_node_id);
  content::RenderFrameHostManager* render_manager =
      frame_tree_node->render_manager();
  content::RenderFrameHost* frame_host = nullptr;
  if (render_manager) {
    frame_host = render_manager->speculative_frame_host();
    if (!frame_host)
      frame_host = render_manager->current_frame_host();
  }
  int frame_process_id = -1, frame_routing_id = -1;
  if (frame_host) {
    frame_process_id = frame_host->GetProcess()->GetID();
    frame_routing_id = frame_host->GetRoutingID();
  }
  bool is_same_document = navigation_handle->IsSameDocument();
  auto url = navigation_handle->GetURL();
  return Emit(event, url, is_same_document, is_main_frame, frame_process_id,
              frame_routing_id);
}
void Ws::BindElectronBrowser(