Defer setAutofill*Detail to frame.js

[darkdh]

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Ran git rebase -i to squash commits (if needed).

fix #4350

Auditors: @bbondy

Test Plan:

1. open about:autofill from about:about
2. add/edit entry should work fine

[bbondy]

++