Add "scaled" property to Crostini app registration.

This new property is used to record a user's preference for display
window scaling. When it's true the app window will be scaled up. This is
used to adjustment some older Linux apps that don't show well on HiDPI
displays.

BUG=chromium:839242
TEST=Unit tests added.

Change-Id: I6bf49b814d4467f09af9143c237d5a4e3984168d
Reviewed-on: https://chromium-review.googlesource.com/1232196
Reviewed-by: Nicholas Verne <nverne@chromium.org>
Commit-Queue: Tim Zheng <timzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592585}
3 files changed