Add chrome/services/app_service design doc

BUG=826982

Change-Id: Icc1398c6c6a87484e8348039c7e7b9b8918d483e
Reviewed-on: https://chromium-review.googlesource.com/c/1328626
Commit-Queue: Nigel Tao <nigeltao@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608256}
1 file changed