https://bugs.webkit.org/show_bug.cgi?id=123374

Reviewed by Eric Carlson.

No tests added; tests will be added when Mock implementations are added in a future patch.

Add new partial interfaces for added methods on AudioTrack, TextTrack, and VideoTrack:
* Modules/mediasource/AudioTrackMediaSource.idl: Add read-only sourceBuffer attribute.
* Modules/mediasource/TextTrackMediaSource.idl: Ditto.
* Modules/mediasource/VideoTrackMediaSource.idl: Ditto.
* Modules/mediasource/AudioTrackMediaSource.h:
(WebCore::AudioTrackMediaSource::sourceBuffer): Added static wrapper around non-static sourceBuffer().
* Modules/mediasource/TextTrackMediaSource.h:
(WebCore::TextTrackMediaSource::sourceBuffer): Ditto.
* Modules/mediasource/VideoTrackMediaSource.h:
(WebCore::VideoTrackMediaSource::sourceBuffer): Ditto.

Add support for writable kind & language attributes through a custom setter:
* bindings/js/JSAudioTrackCustom.cpp:
(WebCore::JSAudioTrack::setKind):
(WebCore::JSAudioTrack::setLanguage):
* bindings/js/JSTextTrackCustom.cpp:
(WebCore::JSTextTrack::setKind):
(WebCore::JSTextTrack::setLanguage):
* bindings/js/JSVideoTrackCustom.cpp:
(WebCore::JSVideoTrack::setKind):
(WebCore::JSVideoTrack::setLanguage):
* html/track/AudioTrack.idl:
* html/track/TextTrack.idl:
* html/track/VideoTrack.idl:

Add setter methods to the implementation classes:
* html/track/TextTrack.cpp:
(WebCore::TextTrack::TextTrack):
(WebCore::TextTrack::setKind):
(WebCore::TextTrack::setLanguage):
* html/track/TextTrack.h:
* html/track/TrackBase.cpp:
(WebCore::TrackBase::TrackBase):
(WebCore::TrackBase::setKind):
(WebCore::TrackBase::setKindInternal):
* html/track/TrackBase.h:
(WebCore::TrackBase::setLanguage):
(WebCore::TrackBase::sourceBuffer):
(WebCore::TrackBase::setSourceBuffer):
* html/track/VideoTrack.cpp:
(WebCore::VideoTrack::VideoTrack):
(WebCore::VideoTrack::setKind):
(WebCore::VideoTrack::setLanguage):
* html/track/VideoTrack.h:

Implement the unimplemented portions of MediaSource and SourceBuffer:
* Modules/mediasource/MediaSource.cpp:
(WebCore::MediaSource::removeSourceBuffer):
* Modules/mediasource/MediaSourceBase.cpp:
(WebCore::MediaSourceBase::MediaSourceBase):
(WebCore::MediaSourceBase::setPrivateAndOpen):
(WebCore::MediaSourceBase::setReadyState):
(WebCore::MediaSourceBase::attachToElement):
* Modules/mediasource/MediaSourceBase.h:
(WebCore::MediaSourceBase::mediaElement):
* Modules/mediasource/SourceBuffer.cpp:
(WebCore::SourceBuffer::videoTracks):
(WebCore::SourceBuffer::audioTracks):
(WebCore::SourceBuffer::textTracks):
(WebCore::SourceBuffer::sourceBufferPrivateDidAddAudioTrack):
(WebCore::SourceBuffer::sourceBufferPrivateDidAddVideoTrack):
(WebCore::SourceBuffer::sourceBufferPrivateDidAddTextTrack):
(WebCore::SourceBuffer::sourceBufferPrivateDidChangeActiveState):
* Modules/mediasource/SourceBuffer.h:
* Modules/mediasource/SourceBuffer.idl:

Add new files to the project:
* DerivedSources.make:
* WebCore.xcodeproj/project.pbxproj:

And a smorgasbord of other utility changes:
* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::loadResource): Pass this when attaching.
(WebCore::HTMLMediaElement::mediaPlayerDidAddTextTrack): Ditto.
* html/HTMLMediaSource.h:
* html/track/TextTrackList.cpp:
(TextTrackList::item): Make const.
* html/track/TextTrackList.h:
(WebCore::TextTrackList::lastItem): Added.
* platform/graphics/InbandTextTrackPrivate.h:
(WebCore::InbandTextTrackPrivate::create): Added.
(WebCore::MockSourceBufferPrivate::trackDidChangeEnabled):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@158821 268f45cc-cd09-0410-ab3c-d52691b4dbfc