[Tizen] Enable context menu settings.

In Tizen specific section 0230: Tizen Settings, it's said: the context menu should
be displayed when the user long-presses, for example, an image, text, or
link. This patch will implement this feature. The related feature is XWALK-1491
window_show_state() and pls add a FIXME comment that this method should go away soon.