[PasswordManager clean-up] Merge copies of CreatePasswordFormFromData
The Mac unit-test had a separate copy of CreatePasswordFormFromData, which did almost the same as the platform-independent version. This CL merges them by replacing the platform-independent instance with the more recently updated Mac copy. It also renames the methods to make clear they are for testing only.
BUG=
451018
Committed:
https://crrev.com/9cd9b02ab72d51bb866b79df523b435230c87be9
Cr-Commit-Position: refs/heads/master@{#315529}