* Electron version: 1.8.2
* Operating system: macos 10.13.3

Reproducing repo: https://github.com/ibash/electron-webkit-app-drag

Demonstrates a bug where `-webkit-app-region: drag` causes a browser view in front of it to miss click events. Oddly - it does not prevent hover events.

Steps:
1. Clone https://github.com/ibash/electron-webkit-app-drag, `yarn install`, `yarn start`
2. Click "button1"
3. Click "button2"

Expected:

Clicking button1 or button2 pops up an alert: "button clicked!"

Actual:

Only clicking button2 pops up an alert: "button clicked!"

atom/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->SetBackgroundOpaque(false);
}
void BrowserWindow::DidFirstVisuallyNonEmptyPaint() {
  if (window_->IsVisible())
    return;
  
  
  const auto view = web_contents()->GetRenderWidgetHostView();
  view->Show();
  view->SetSize(window_->GetContentSize());
  
  base::ThreadTaskRunnerHandle::Get()->PostTask(
      FROM_HERE,
      base::Bind([](base::WeakPtr<BrowserWindow> self) {
        if (self)
          self->Emit("ready-to-show");
      }, GetWeakPtr()));
}
void BrowserWindow::BeforeUnloadDialogCancelled() {