Issue golang/go#42212 manifests as test timeouts, and is by far the most
frequent of these known issues.

Issue golang/go#51001 causes failures with "systemstack called from unexpected
goroutine". It seems to have been introduced sometime last year, but
it isn't clear to me whether it is a regression or an older (latent)
bug unearthed by some other change.

Issue golang/go#52724 appears to be a bug or race in the Android emulator
itself. It might require a builder image update and/or escalation to
the maintainers of the emulator proper.

Updates golang/go#53377.

Change-Id: I677915b1ff02dd02e0f14c63b0d25caf11e27a72
Reviewed-on: https://go-review.googlesource.com/c/build/+/412174
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>

I had initially added known issues fairly aggressively in order to use
them to reduce noise in 'greplogs -triage'. Now that we are using
'watchflakes' for triage, that noise reduction is no longer important
(the failures are already clustered to their respective known issues),
and having greyed-out cells on the dashboard makes new regressions too
easy to miss.

Concretely:

- golang/go#42212 is mostly specific to x/net at this point (as
  golang/go#57841)

- There have been no failures matching golang/go#51001 since October.

- golang/go#52724 has been so rare lately that we hadn't yet added a
  'watchflakes' pattern for it.

- There have been no failures matching golang/go#51443 since May.

- There have been no failures matching golang/go#53116 or
  golang/go#53093 since I enabled 'watchflakes' for the builder in
  December.

- The linux-amd64-perf builder seems to be passing consistently for
  x/benchmarks and x/tools, so there is no need to refer to
  golang/go#53538 to explain failures on it.

Change-Id: Ia16db2a23e5fa037a299f1f56fb26f1cf84521e1
Reviewed-on: https://go-review.googlesource.com/c/build/+/465156
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>