Using these methods to compute block offsets instead of the block
layout info could lead to some confusion.

Change-Id: Iaa3b91bdb517632107923076e3ece7efeab278c2
Reviewed-on: https://chromium-review.googlesource.com/321250
Tryjob-Request: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>