All tracks now have a MediaSource member with associated functions.
TextTrackList provides a lastItem function.
Keep using KURL for now.
Slight changes in the API, inherit from URLRegistry.
Expose some new public APIs.
Use new API from MediaSourceRegistry.
Backport from trunk.
Backport from trunk. This new version uses a layered implementation with platform specifics.
Try to provide the usual API to work with iterators.
Backport trunk code trying to use our "old" API.
Fix prototype.