The priority scheduler allows stream starvation (see golang/go#58804)
and is CPU intensive. In addition, the RFC 7540 prioritization
scheme it implements was deprecated in RFC 9113 and does not appear
to have ever had significant adoption.
Add a simple round-robin scheduler and enable it by default.
For golang/go#58804
Change-Id: I5c5143aa9bc339fc0894f70d773fa7c0d7d87eef
Reviewed-on: https://go-review.googlesource.com/c/net/+/478735
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Damien Neil <dneil@google.com>