[DL] Reject the promise if it's acquired while connected.

This patch ensures that we don't accidentally use display locking in
mode 1, which isn't currently supported.

R=chrishtr@chromium.org

Bug: 882663
Change-Id: I2be26e2573ebe93a97bd6df4c8fcb7cd6221b28c
Reviewed-on: https://chromium-review.googlesource.com/c/1347102
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#611859}
2 files changed