After creating a notification and passing a tag, then subsequent notifications with the same tag don't show up for the entire lifespan of the app.

* Electron version: 1.8.1
* Operating system: Windows 7 x64

### Expected behavior

New notifications should open after the last one has closed.

### Actual behavior

Nothing happens

### How to reproduce

  $ git clone https://github.com/electron/electron-quick-start .
  $ npm install
  $ npm start

Then in the app open dev tools and paste this in the console:

    new Notification("test", { tag: "test" });

Wait for the notification to disappear and paste it again, observe nothingness.
atom/browser/notifications/win/win32_desktop_notifications/toast.cc
Draw();
  if (IsWindowVisible(hwnd_)) {
    RECT rc;
    GetWindowRect(hwnd_, &rc);
    POINT origin = {0, 0};
    SIZE size = {rc.right - rc.left, rc.bottom - rc.top};
    UpdateLayeredWindow(hwnd_, NULL, nullptr, &size, hdc_, &origin, 0, nullptr,
                        0);
  }
}
void DesktopNotificationController::Toast::Dismiss() {
  if (!is_non_interactive_) {
    
    
    
    is_non_interactive_ = true;
    AutoDismiss();
  }
}
void DesktopNotificationController::Toast::AutoDismiss() {
  KillTimer(hwnd_, TimerID_AutoDismiss);
  StartEaseOut();
}
void DesktopNotificationController::Toast::CancelDismiss() {
  KillTimer(hwnd_, TimerID_AutoDismiss);
  ease_out_active_ = false;
  ease_out_pos_ = 0;
}
void DesktopNotificationController::Toast::ScheduleDismissal() {