Event message boxes and MSE SourceBuffer range removal

[chrisn]

MSE SourceBuffer.remove(start, end) allows the web application to remove media for a given time range.

What should happen to event message boxes that are on the media timeline?

• Event messages that start and end before the start of the time range to be removed
• Event messages that start after the end of the time range to be removed
• Event message that are fully contained within the time range to be removed
• Event messages that overlap the time range to be removed

See discussion 22/3/2021