Fixes   #31747.
Updates #19308.
Updates #12711.
Updates #29008.
Updates #28493.
Updates #19113.

Change-Id: I76d2fdbc7698cc4e0f31b7ae24cbb4d28afbb6a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/174897
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>