* 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
mate::Arguments* args) {
  std::string display_name;
  if (!args->GetNext(&display_name))
    display_name = path;
  window_->PreviewFile(path, display_name);
}
void BrowserWindow::CloseFilePreview() {
  window_->CloseFilePreview();
}
void BrowserWindow::SetParentWindow(v8::Local<v8::Value> value,
                             mate::Arguments* args) {
  if (IsModal()) {
    args->ThrowError("Can not be called for modal window");
    return;
  }
  mate::Handle<BrowserWindow> parent;
  if (value->IsNull() || value->IsUndefined()) {
    RemoveFromParentChildWindows();
    parent_window_.Reset();
    window_->SetParentWindow(nullptr);
  } else if (mate::ConvertFromV8(isolate(), value, &parent)) {
    parent_window_.Reset(isolate(), value);
    window_->SetParentWindow(parent->window_.get());
    parent->child_windows_.Set(isolate(), ID(), GetWrapper());
  } else {
    args->ThrowError("Must pass BrowserWindow instance or null");
  }
}
v8::Local<v8::Value> BrowserWindow::GetParentWindow() const {