Implement VTTCue.region and sync the VTTRegion interface
This CL implements the VTTCue.region property, replacing 'regionId'. The
main implementation mechanism is a new map in VTTParser that tracks the
regions currently seen.
Rewrite the region parser test to be based on cues rather than the list
of regions. This will ease the removal of TextTrack.regions.
Sync the VTTRegion with the current spec by
* renaming the 'height' property to 'lines',
* adding and using the ScrollSetting IDL enumeration type and
* dropping the 'id' and 'track' properties.
Update tests as needed to match the above changes.
BUG=690014
Review-Url: https://codereview.chromium.org/2682333002
Cr-Commit-Position: refs/heads/master@{#449589}
16 files changed
