GitLab

The delay to start updating the wallpaper after rotating the screen used
to be 2 seconds which was also accompanied by unnecessary clearing of
the wallpaper cache resulting in an ugly visual effect.

Now we reduced the delay to only 100 ms and we only clear the cache when
we add another display.

BUG=359654
TEST=manual

Review URL: https://codereview.chromium.org/1131243006

Cr-Commit-Position: refs/heads/master@{#329507}