GitLab

Add power.lock_screen_dim_delay_ms and
power.lock_screen_off_delay_ms prefs that provide alternate
screen-dim and screen-off inactivity delays that are honored
while the screen is locked. They currently default to 30 and
40 seconds, respectively.

BUG=190499

Review URL: https://codereview.chromium.org/793973002

Cr-Commit-Position: refs/heads/master@{#308131}