### Issue Details

* **Electron Version:**
  * 3.0.x, 4.0.x, 5.0.x, 6.0.x
* **Operating System:**
  * macOS 10.14.5
* **Last Known Working Electron version:**
  * 2.0.x

### Expected Behavior
`BrowserWindow.on('swipe')` fires when doing a 3-finger swipe gesture.

### Actual Behavior
`BrowserWindow.on('swipe')` does not fire.

shell/browser/api/atom_api_browser_window.cc
content::RenderViewHost* render_view_host) {
  if (!window()->transparent())
    return;
  content::RenderWidgetHostImpl* impl = content::RenderWidgetHostImpl::FromID(
      render_view_host->GetProcess()->GetID(),
      render_view_host->GetRoutingID());
  if (impl)
    impl->owner_delegate()->SetBackgroundOpaque(false);
}
void BrowserWindow::DidFirstVisuallyNonEmptyPaint() {
  if (window()->IsVisible())
    return;
  
  
  auto* const view = web_contents()->GetRenderWidgetHostView();
  view->Show();
  view->SetSize(window()->GetContentSize());
  
  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE, base::BindOnce(
                     [](base::WeakPtr<BrowserWindow> self) {
                       if (self)
                         self->Emit("ready-to-show");
                     },
                     GetWeakPtr()));
}
void BrowserWindow::BeforeUnloadDialogCancelled() {