Prune CreateVisibleSelectionDeprecated from unit test files
This patch also adds DCHECKs to createVisibleSelection to prevent callers
from passing null base and non-null extent, which does not make sense.
BUG=
651373
Committed:
https://crrev.com/b84e284987d122603226db600a398a9cbe235f62
Cr-Commit-Position: refs/heads/master@{#422049}