Before this CL, a SACK was generated from scratch based on information
about each received fragment, to generate correct gap-ack-blocks.
When there was a lot of data in the data tracker (due to packet loss),
this took considerate time, as generating a SACK was O(N), where N is
the amount of fragments in the data tracker.
By instead having precomputed gap-ack-blocks that are continuously
updated, generating a SACK is much faster and the memory usage goes down
a bit as well.
Bug: webrtc:12799
Change-Id: I924752c1d6d31f06d27246e10b595e9ccb19320f
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/220763
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34171}
27d2be3583