Add DriveFS to about:flags.

Also move the DriveFS feature to a more common location in
chromeos/chromeos_features.h.

Bug: 859800
Change-Id: Iffffea69c4874ae0583c67e8a8e6a9b50a4951e4
Reviewed-on: https://chromium-review.googlesource.com/1124211
Reviewed-by: Stuart Langley <[email protected]>
Reviewed-by: Noel Gordon <[email protected]>
Commit-Queue: Sam McNally <[email protected]>
Cr-Commit-Position: refs/heads/master@{#572459}
10 files changed