[Mac] in-band cues sometimes have incorrect duration

[Mac] in-band cues sometimes have incorrect duration
https://bugs.webkit.org/show_bug.cgi?id=115200

Reviewed by Jer Noble.

No new tests, this is not possible to test in DRT.

* html/track/InbandTextTrack.cpp:
(WebCore::InbandTextTrack::addGenericCue): Don't add completed cues to the map.
(WebCore::InbandTextTrack::removeGenericCue): Log when a cue is removed from the track.

* platform/graphics/avfoundation/InbandTextTrackPrivateAVF.cpp:
(WebCore::InbandTextTrackPrivateAVF::InbandTextTrackPrivateAVF): Initialize m_pendingCueStatus.
(WebCore::InbandTextTrackPrivateAVF::processCue): Never call update() on a cue that is delivered
    while seeking.
(WebCore::InbandTextTrackPrivateAVF::beginSeeking): Flush all incomplete cues, remember that
    we are seeking.
(WebCore::InbandTextTrackPrivateAVF::resetCueValues):
* platform/graphics/avfoundation/InbandTextTrackPrivateAVF.h:

* platform/graphics/avfoundation/MediaPlayerPrivateAVFoundation.cpp:
(WebCore::MediaPlayerPrivateAVFoundation::seek): Call track->beginSeeking() instead of resetCueValues().
(WebCore::MediaPlayerPrivateAVFoundation::seekCompleted): Call track->endSeeking().

* platform/graphics/avfoundation/objc/InbandTextTrackPrivateAVFObjC.mm:
(WebCore::InbandTextTrackPrivateAVFObjC::kind): Include class name in Kind enum values to
    avoid compile error.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@149187 268f45cc-cd09-0410-ab3c-d52691b4dbfc