CrOS: add first draft of an App Service app list model

Just names and icons for now. More features will come in future commits.

Tested manually, with "chrome --enable-features=AppService".

BUG=826982

Change-Id: I465daa7597e5172792d185e8b33228b127879057
Reviewed-on: https://chromium-review.googlesource.com/c/1349155
Commit-Queue: Nigel Tao <nigeltao@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612003}
10 files changed