Get rid of the Mojo message ShowManualFallbackForSaving in PasswordManagerClient.

- The method is useless because it should only be called in response to
UserTriggeredGeneratePassword.
- PasswordManagerClient Mojo interface was renamed as it describes password
generation.

Bug: 845458
Change-Id: I638945168fe31cfe7284219e3fc212de6c33fa7b
Reviewed-on: https://chromium-review.googlesource.com/c/1426789
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Reviewed-by: Dominic Battré <battre@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625601}
15 files changed