[MSE][Mac] Add AVSampleBufferRendererSynchronizer support.

[MSE][Mac] Add AVSampleBufferRendererSynchronizer support.
https://bugs.webkit.org/show_bug.cgi?id=125954

Reviewed by NOBODY (OOPS!).

Instead of slaving all the various renderer's CMTimebases to one master timebase,
use AVSampleBufferRenderSynchronizer, which essentially does the same thing.

* platform/graphics/avfoundation/objc/MediaPlayerPrivateMediaSourceAVFObjC.h:
* platform/graphics/avfoundation/objc/MediaPlayerPrivateMediaSourceAVFObjC.mm:
(WebCore::CMTimebaseEffectiveRateChangedCallback): Added; call effectiveRateChanged().
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::MediaPlayerPrivateMediaSourceAVFObjC): Set up
    the synchronizer and all the observers.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::~MediaPlayerPrivateMediaSourceAVFObjC): Tear down
    the same.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::isAvailable): Require the
    AVSampleBufferRenderSynchronizer class.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::playInternal): Convert Clock -> Synchronizer.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::pauseInternal): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::paused): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::currentTimeDouble): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::seekInternal): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::setRateDouble): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::ensureLayer): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::destroyLayer): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::effectiveRateChanged): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::addDisplayLayer): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::removeDisplayLayer): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::addAudioRenderer): Ditto.
(WebCore::MediaPlayerPrivateMediaSourceAVFObjC::removeAudioRenderer): Ditto.

Drive-by fix; audio samples can't be subdivided, and video samples are
rarely combined, so remove the call to CMSampleBufferCallForEachSample:
* platform/graphics/avfoundation/objc/SourceBufferPrivateAVFObjC.mm:
(WebCore::SourceBufferPrivateAVFObjC::didProvideMediaDataForTrackID):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@160825 268f45cc-cd09-0410-ab3c-d52691b4dbfc