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 (uia_) {
    auto* UiaDisconnectProvider =
        reinterpret_cast<decltype(&::UiaDisconnectProvider)>(GetProcAddress(
            GetModuleHandle(L"uiautomationcore.dll"), "UiaDisconnectProvider"));
    
    
    
    uia_->DetachToast();
    if (UiaDisconnectProvider)
      UiaDisconnectProvider(uia_);
    uia_->Release();
    uia_ = nullptr;
  }
  DeleteDC(hdc_);
  if (bitmap_)
    DeleteBitmap(bitmap_);
  if (scaled_image_)
    DeleteBitmap(scaled_image_);
}
void DesktopNotificationController::Toast::Register(HINSTANCE hinstance) {
  WNDCLASSEX wc = {sizeof(wc)};
  wc.lpfnWndProc = &Toast::WndProc;
  wc.lpszClassName = class_name_;
  wc.cbWndExtra = sizeof(Toast*);
  wc.hInstance = hinstance;
  wc.hCursor = LoadCursor(NULL, IDC_ARROW);
  RegisterClassEx(&wc);
}
LRESULT DesktopNotificationController::Toast::WndProc(HWND hwnd,