Backward seek issue with HLS live stream

[jaranflaath]

Issue description

Working on the radio app for Denmark Radio, we discovered an issue with seeking in live HLS stream. We start playing a stream, then jump to about midways into the stream, then start skipping backwards. ExoPlayer will then have trouble skipping more than a second or two, perhaps managing to skip 15 seconds one time, before it gives up and start skipping forward instead - eventually a minute or more for each click on the backward skip button. The issue has been reproduced in the demo app of the ExoPlayer library.

Reproduction steps

I have forked the library and modified the demo app to reproduce the issue. The fork is available here: https://github.com/jaranflaath/ExoPlayer/tree/live_stream_seeking_bug

I have added a new HLS source, "DR Radio". To reproduce the issue, follow these steps:

1. Start the stream "DR Radio" under HLS in the demo app
2. Scrub the progress bar to around 12 minutes
3. Skip forward a few times - works fine
4. Skip backwards, and you will notice the progress is having problems skipping and will eventually start skipping forward in large chunks on up to 1.5 minutes.

Link to test content

Sent by email

Version of ExoPlayer being used

Reproduced in versions 2.7.1->2.7.3. Works fine in 2.7.0

Device(s) and version(s) of Android being used

Tested on Pixel 2 XL with Android 8.1, as well as emulator running Android 8.1

A full bug report captured from the device

Not relevant in this case.

[AquilesCanta]

This is indeed a regression. A fix will be provided in the next push.

[jaranflaath]

Looking forward to the fix :)