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
ULONG duration;
  if (!SystemParametersInfo(SPI_GETMESSAGEDURATION, 0, &duration, 0)) {
    duration = 5;
  }
  SetTimer(hwnd_, TimerID_AutoDismiss, duration * 1000, nullptr);
}
void DesktopNotificationController::Toast::ResetContents() {
  if (scaled_image_) {
    DeleteBitmap(scaled_image_);
    scaled_image_ = NULL;
  }
  Invalidate();
}
void DesktopNotificationController::Toast::PopUp(int y) {
  vertical_pos_target_ = vertical_pos_ = y;
  StartEaseIn();
}
void DesktopNotificationController::Toast::SetVerticalPosition(int y) {
  
  if (y == vertical_pos_target_)
    return;
  
  vertical_pos_ += static_cast<int>((vertical_pos_target_ - vertical_pos_) *
                                    stack_collapse_pos_);
  
  vertical_pos_target_ = y;
  stack_collapse_start_ = GetTickCount();
  data_->controller->StartAnimation();
}
HDWP DesktopNotificationController::Toast::Animate(HDWP hdwp,