GitLab

Given the PhoneHub notification data, this CL fills in the created CrOS
corresponding notification's details:
  * timestamp
  * icons and images
  * priority
  * inline reply button

Screenshot:
https://screenshot.googleplex.com/8bhJVzvqFmPcufT.png

BUG=1128091,1106937

Change-Id: I82d64c1bb01235bb1dc64fab0b29cd00b3bef1a0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2418557
Commit-Queue: Tim Song <tengs@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808810}