[FlashFrame] change NativeWindow::FlashFrame input parameter to int, the javascript boolean parameter true redirected as -1, false as 0

[FlashFrame] change NativeWindow::FlashFrame input parameter to int, the javascript boolean parameter true redirected as -1, false as 0

so on windows we can specify how many time to flash frame
and on OSX we can choose between NSInformationalRequest / NSCriticalRequest

Intend with 2 spaces