user32: Partially implement FlashWindowEx with tests

[Dmitry Timoshkov]

André Hentschel <nerv at dawncrow.de> wrote:

> +    if (!pfwi->hwnd || pfwi->cbSize < sizeof(FLASHWINFO))
> +    {
> +        SetLastError(ERROR_INVALID_PARAMETER);
> +        return FALSE;
> +    }

I don't see in your tests the case for 'cbSize > sizeof(FLASHWINFO)'.
Also using !IsWindow() instead of !hwnd would fix one more test case.

-- 
Dmitry.