Declare more key systems as supported. (ClearKey and Youtube PR).
Add the MSE include dir when enabled
Add missing function
Use the correct interface
Start backporting
Refactoring

Remove more auto keywords
Remove all unique_ptr keywords
Remove every occurence of auto
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.
Port more operators to MediaTime class
Use the correct type