Remove PasswordStore::AuthorizationPromptPolicy

The only value of this enum used in production code since we dropped the MacOS
Keychain support was "DISALLOW_PROMPT". This CL removes the whole enum.

The connection to bug 582087 is that this CL simplifies the signature of GetLogins, which is related to fixing that bug.

This CL also fixes two missing braces pointed out by git cl lint.

R=vasilii@chromium.org
BUG=582087,466638

Review URL: https://codereview.chromium.org/1730313004

Cr-Commit-Position: refs/heads/master@{#377853}
29 files changed