This reverts commit 9335363789.
Reason for revert: It's full of code accessing AbstractBlock::mReason
out there, see [1]. Also, it was never hard deprecated. While that may
be acceptable under some circumstances, it's definitely not OK to remove
code when there are consumers around. I'd have fixed it right now without
reverting if it were a single repo, but there's just too many.
[1] - https://codesearch.wmflabs.org/search/?q=-%3EmReason&i=nope&files=&repos=
Change-Id: I8669f502b50cff89e28dada0f65fe2b130ae9b37