[iOS Media] Airplay button should be blue when active

[iOS Media] Airplay button should be blue when active
https://bugs.webkit.org/show_bug.cgi?id=142193

Reviewed by Brent Fulgham.

Add a blue form of the Airplay button that is used
when we are actively displaying on another screen.

* Modules/mediacontrols/mediaControlsiOS.css:
(video::-webkit-media-controls-wireless-playback-picker-button):
(video::-webkit-media-controls-wireless-playback-picker-button:active):
(video::-webkit-media-controls-wireless-playback-picker-button.playing):
* Modules/mediacontrols/mediaControlsiOS.js:
(ControllerIOS.prototype.updateWirelessPlaybackStatus):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@180906 268f45cc-cd09-0410-ab3c-d52691b4dbfc