GitLab

Survey base/task_scheduler for remaining unprefixed "BACKGROUND" strings
referring to task priority (i.e. not referring to
"background thread priority").

Best-effort survey of the codebase for "BACKGROUND priority" left behind
in comments.

Update docs and remove TaskPriority::BACKGROUND for good

TBR=robliao@chromium.org

Bug: 863341
Change-Id: I055ac623767c1d77895d78dbf544a2d781a6637d
Reviewed-on: https://chromium-review.googlesource.com/1153461
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578802}