Fix compile warnings with attributes. BUG=angle:676 Change-Id: I291c0b618854179f726cb4c969fb65182d3b591e Reviewed-on: https://chromium-review.googlesource.com/204340 Tested-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shannon Woods <shannonwoods@chromium.org>