[iOS][MF] Show an alert when a field won't be filled

Only fill credit cards on HTTPS, and passwords on HTTPS and password
fields. Show an alert to the user otherwise.

Bug: 905652, 878388, 845472
Change-Id: I51e0f07757dc4f7f1e002b88b83a2d2eeea071b5
Reviewed-on: https://chromium-review.googlesource.com/c/1340259
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609980}
11 files changed