This may have made more sense in the old module design (where
"unification" was a thing), but as-is it's only used for a few
asserts in debug mode. These asserts don't make much sense inside
ModuleDescriptor; instead, as the modules implementation is fleshed
out, I expect the appropriate replacement asserts to show up at the
use of the ModuleDescriptor.

Review URL: https://codereview.chromium.org/1598433006

Cr-Commit-Position: refs/heads/master@{#33345}