Media gets stuck on lowest bandwidth tracks.

[sanbornhilland]

Using latest from master (f7fd3c9)

1. Loading a live stream we have I can see that occasionally in shaka.abr.SimpleAbrManager.prototype.segmentDownloaded we get a segment with the same endTimeMs and startTimeMs, resulting in a durationMs of 0.
2. This produces as bandwidth of Infinity in shaka.abr.EwmaBandwidthEstimator.prototype.sample.
3. When shaka.abr.Ewma.prototype.sample is called with 0 and Infinity it produces an estimate of NaN because: value * (1 - adjAlpha) = Infinity * (1 - 1) = NaN;
4. this.estimate_ is set to NaN and subsequently every sample after this return NaN

Result:

ABR fails and the media gets stuck on the lowest tracks.

Expected:

Sampling should ignore bad values and move on.

[joeyparrish]

Thanks for the report and the PR. Much appreciated!