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This CL uses the BackgroundTaskCoordinator to scedule background task
with platform API.

Bug: 963283,930968
Change-Id: I9d6af682cdc456f66dcab88997eee08acab11320
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1639560
Commit-Queue: Xing Liu <xingliu@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666112}