Implement password suggestion in //ios/web_view

Bug: 865114
Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I0a7d78359724a4e4cdca350145b55b65e5d4f184
Reviewed-on: https://chromium-review.googlesource.com/c/1250503
Commit-Queue: Scott Wu <scottwu@chromium.org>
Reviewed-by: Hiroshi Ichikawa <ichikawa@chromium.org>
Reviewed-by: John Wu <jzw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600341}
9 files changed