GitLab

This CL adds:
* chrome.printing API setup including new "printing" permission and
printing.idl API description,
* One event: OnJobStatusChanged() and its implementation,
* Unit tests for this event,
* New print job source: EXTENSION. It's not used in print job creation
yet but is required for correct implementation of the event.

This CL doesn't add any API test since it's impossible yet to create
print job via API. API test covering this event will be added together
with submitJob() function implementation in follow-up CL.

Bug: 996785
Change-Id: I1708631caffdde2395a3d07f2ea7de392d09a63f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1824948Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Sean Kau <skau@chromium.org>
Commit-Queue: Nikita Podguzov <nikitapodguzov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710698}