The modules in x/mobile are still tested under Go 1.16, which emits a vet warning for files that have "//go:build" constraint comments without matching "// +build" comments. This fixes a build failure observed on the Go dashboard: https://build.golang.org/log/2925343437d0c0559bcfa9d9de740a3a1aef2dc3 Change-Id: Ic0e3ed151a2ea3262d853c4e22cf042d54230ede Reviewed-on: https://go-review.googlesource.com/c/mobile/+/362575 Trust: Bryan C. Mills <bcmills@google.com> Run-TryBot: Bryan C. Mills <bcmills@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>