[Mac] update in-band caption attributes
https://bugs.webkit.org/show_bug.cgi?id=116057

Reviewed by Dean Jackson.

* html/track/InbandTextTrack.cpp:
(WebCore::InbandTextTrack::updateCueFromCueData): Copy highlight color.

* html/track/TextTrackCueGeneric.cpp:
(WebCore::TextTrackCueGenericBoxElement::applyCSSProperties): "highlight" color sets the cue
    background, "background" color sets the cue container background.
* html/track/TextTrackCueGeneric.h:

* platform/graphics/InbandTextTrackPrivateClient.h:

* platform/graphics/avfoundation/InbandTextTrackPrivateAVF.cpp:
(WebCore::InbandTextTrackPrivateAVF::processCueAttributes): Process "highlight" color.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@150055 268f45cc-cd09-0410-ab3c-d52691b4dbfc