[Chrome OS] Implement the device wallpaper policy.
This CL implements the device policy to allow the domain admins to
set a device level policy controlled wallpaper for an enterprise
managed device. The device policy wallpaper will display on the login
screen all the time without requiring a user to log in. The device
policy wallpaper is also set as a user's wallpaper if there is no user
policy controlled wallpaper and the user hasn't changed his default
wallpaper in a user's session.
Detailed description of the expected behavior is described as below:
- In the login screen, if the device wallpaper policy present, use the
device policy wallpaper, otherwise, check if user-selected wallpaper
exists, if so, use the user-selected wallpaper, otherwise use OEM
default wallpaper.
- Within a user session, if the user wallpaper policy present, user the
user policy wallpaper, otherwise, check if user has changed his default
wallpaper before, if so, use user-slected wallpaper, otherwise, check
if the device wallpaper policy present, if so, use the device policy
wallpaper, otherwise, use OEM default wallpaper.
This is a follow-up CL of https://codereview.chromium.org/2544693002/.
BUG=475998
Review-Url: https://codereview.chromium.org/2572793003
Cr-Commit-Position: refs/heads/master@{#438667}
7 files changed
