[Files app] Simplified FileManager

Used Promises, async and await where it makes sense.
Removed the use of AsyncUtil.Queue from setupCurrentDirectory_().

Change-Id: I58281408c1bc3f6f1f9c6216d4862c88e393ef9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1626838
Auto-Submit: François Degros <fdegros@chromium.org>
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/master@{#663449}
2 files changed