This updates 'hello-world.cc' sample.

Change-Id: Id1f3fd222ddd89946e3ab50a8eff5c6477d1f665
Reviewed-on: https://chromium-review.googlesource.com/1089816
Commit-Queue: Ben Smith <binji@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53597}