gl: fix build
gl: fix build

Change-Id: If3888b1795ca4c701f99e2021bcac4e860f96b7b
Reviewed-on: https://go-review.googlesource.com/17774
Reviewed-by: David Crawshaw <a2f0bf29257797dd66800b4fbb9945c3e216c004@golang.org>

golang/mobile,golang/mobile,golang/mobile,golang/mobile