Recent Clang versions (r317076+) warn about this.

Bug: chromium:780523
Change-Id: Iccc8d675ce4700f67dedfaa60bc6662b03b55ceb
Reviewed-on: https://chromium-review.googlesource.com/749117Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49066}