Make merged segment size configurable

[lemondoglol]

This change is related to this request google/ExoPlayer#10949

For making MAX_MERGED_SEGMENT_START_TIME_DIFF_US configurable

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[lemondoglol]

morning @marcbaechinger ! Could you review this when you have time? Thanks so much! (I can't assign this PR to you as a reviewer somehow)

[marcbaechinger]

Many thanks!

I've added my comments. Most are nits. If you want to update your PR accordingly that would be great! Else I'd proceed sooner or later and apply the changes myself before I give into internal review and submit. :)

Thanks for your contribution!

[marcbaechinger]

please make it a final member field, rename to maxMergedSegmentStartTimeDiffUs and move to the group of private final fields around L89.

[lemondoglol]

maxMergedSegmentStartTimeDiffUs can't be final. And if we make it final, then it would give error in constructor where we modify this field.

And it needs to be static, since it is being used in static method (and since it needs to be static, so we would need to give an initial value to it).

Please let me know if I misunderstand your comment

[marcbaechinger]

Ah I get it. mergeSegments is static.

We still want it as a member field of the downloader. We pass the value into the static method mergeSegments as an additional param then.

[lemondoglol]

okay, so modified the mergeSegments parameters, now it can be non-static and be final