Linux native notifications: Add suppress-sound hint when notification is silent

BUG=676220
R=peter@chromium.org
CC=thestig@chromium.org

Change-Id: I20a4a246b89f8be56bfdffcbfb7b7c38be203eaa
Reviewed-on: https://chromium-review.googlesource.com/687887
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505165}
2 files changed