[scheduling] Use ScopedTaskEnvironment instead of MessageLoop in cloud_print

MessageLoop will go away, eventually.

BUG=891670

Change-Id: Id593e33312007602c236f9f0452a0b6cb0ed4bd4
Reviewed-on: https://chromium-review.googlesource.com/c/1451921
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Carlos Caballero <carlscab@google.com>
Cr-Commit-Position: refs/heads/master@{#628809}
1 file changed