GitLab

This CL implements the storage mechanism for the images in
AccountTrackerService. Images are save to and loaded from
disk.

Bug: 794522
Change-Id: I6e54b5467e11d8f32a8518ab042218e74914ca3c
Reviewed-on: https://chromium-review.googlesource.com/913575Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Thomas Tangl <tangltom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536693}