No test as I couldn't figure out how to persuade gradle test to
strip classes.
Fixesgolang/go#30251
Change-Id: I7dca9169a4a8eb31b981ad49047a6bdfa6f6efd7
Reviewed-on: https://go-review.googlesource.com/c/164798
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>