* 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
std::string type;
  args->GetNext(&type);
  auto* render_view_host = web_contents()->GetRenderViewHost();
  if (render_view_host) {
    auto* impl = content::RenderWidgetHostImpl::FromID(
        render_view_host->GetProcess()->GetID(),
        render_view_host->GetRoutingID());
    if (impl)
      impl->SetBackgroundOpaque(type.empty() ? !window_->transparent() : false);
  }
  window_->SetVibrancy(type);
}
void BrowserWindow::SetTouchBar(
    const std::vector<mate::PersistentDictionary>& items) {
  window_->SetTouchBar(items);
}
void BrowserWindow::RefreshTouchBarItem(const std::string& item_id) {
  window_->RefreshTouchBarItem(item_id);
}
void BrowserWindow::SetEscapeTouchBarItem(
    const mate::PersistentDictionary& item) {
  window_->SetEscapeTouchBarItem(item);
}
int32_t BrowserWindow::ID() const {
  return weak_map_id();
}
v8::Local<v8::Value> BrowserWindow::WebContents(v8::Isolate* isolate) {