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
if (!inst->ease_out_active_ && inst->ease_in_pos_ == 1.0f)
        inst->ScheduleDismissal();
      
      inst->data_->controller->StartAnimation();
    }
      return 0;
    case WM_WINDOWPOSCHANGED: {
      auto*& wp = reinterpret_cast<WINDOWPOS*&>(lparam);
      if (wp->flags & SWP_HIDEWINDOW) {
        if (!IsWindowVisible(hwnd))
          Get(hwnd)->is_highlighted_ = false;
      }
    } break;
    case WM_GETOBJECT:
      if (lparam == UiaRootObjectId) {
        auto* inst = Get(hwnd);
        if (!inst->uia_) {
          inst->uia_ = new UIAutomationInterface(inst);
          inst->uia_->AddRef();
        }
        
        if (!inst->uia_->IsDetached()) {
          return UiaReturnRawElementProvider(hwnd, wparam, lparam, inst->uia_);
        }
      }
      break;
  }
  return DefWindowProc(hwnd, message, wparam, lparam);
}
HWND DesktopNotificationController::Toast::Create(