git cl land + gnumbd: add asserts.
git cl land + gnumbd: add asserts.

BUG=642493

Change-Id: Ib1234922e4bcd4ee286fffb8f7c637e4d2442a42
Reviewed-on: https://chromium-review.googlesource.com/414504
Commit-Queue: Andrii Shyshkalov <a30c74fa30536fe7ea81ed6dec202e35e149e1fd@chromium.org>
Reviewed-by: Sergiy Byelozyorov <aadb4a11584aa9878242ea5d9e4b7e3429654579@chromium.org>

CoherentLabs/depot_tools,CoherentLabs/depot_tools