Prevent jumpy timeline when doing multiple quick successive seeks with HLS video

[karendolan]

The jumpy timeline on rapid skip button clicks happens in Chrome browser.

TMI: Hi UPV, Last summer I overrode UPV's mp4 and HLS code to solve some issues with our site's HLS videos. One of them was an issue with a jumpy timeline and chaotic video seek behaviour when someone vigorously clicks the seek forward or seek backward several times sequentially on a multi-video event. Yes, this is a real student use case.

The new UPV code still has the issue. After a dissecting my old code, applying and testing parts, the 3 lines of code in this pull resolved the issue locally. I will continue testing because I don't get why this works. But, it can't hurt, so here it is.

To duplicate the issue:

• Go to: https://paellaplayer.upv.es/player.html?id=hls-multiquality
• Play the video, then click the seek forward button quickly multiple times.
• EXPECTED: the video seeking is smooth and the timeline/current time doesn't jump around
• ACTUAL: the video seeking get chaotic and the timeline jumps back and forth before all the seeks are resolved