As discussed in person, it may be cleaner to introduce a new flag such that
- autofilled (existing flag) is interpreted as filled on page load
- user assisted autofilled (new flag) is interpreted as filled from account picker

If Chrome fills a credential on page load and the user picks a different account, both flags would be set.

I've shared https://docs.google.com/document/d/1VOtG9PoxRFUzx-jJQ_mgExhfwQqhp7Wt5KxptWnjJKI/edit#heading=h.guj5jltd293w and proceeding to make the changes.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1fdadcba612f7b1c5697fc82010f3df80e7da392

commit 1fdadcba612f7b1c5697fc82010f3df80e7da392
Author: Christos Froussios <cfroussios@chromium.org>
Date: Fri Aug 10 12:02:58 2018

[Password Manager] Split AUTOFILLED field flag

The flag currently indicates that the field was autofilled, regardless
of the trigger for autofilling.

We will now identify two triggers separately.
1. AUTOFILLED_ON_USER_TRIGGER. This refers to Fill On Account Select in
the context of the password manager. It also the current default
behaviour for Autofill.
2. AUTOFILLED_ON_PAGELOAD. Password manager determined that a password
form is a login form and filled the credentials as soon as the page was
loaded.

Any conditions which took AUTOFILLED into account are made to work with
either of the new flags.

Bug:  867348 
Change-Id: I2eb5fea7219ce784822174de24e76b3e1e4f1f15
Reviewed-on: https://chromium-review.googlesource.com/1169060
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582121}
[modify] https://crrev.com/1fdadcba612f7b1c5697fc82010f3df80e7da392/components/autofill/content/renderer/password_autofill_agent.cc
[modify] https://crrev.com/1fdadcba612f7b1c5697fc82010f3df80e7da392/components/autofill/core/common/form_field_data.h
[modify] https://crrev.com/1fdadcba612f7b1c5697fc82010f3df80e7da392/components/password_manager/core/browser/browser_save_password_progress_logger.cc
[modify] https://crrev.com/1fdadcba612f7b1c5697fc82010f3df80e7da392/components/password_manager/core/browser/form_parsing/form_parser_unittest.cc

+kolos FYI

Hi! We would like to merge r582121 into beta. The CL has been on trunk for a few days already.

This bug requires manual review: M69 has already been promoted to the beta branch, so this requires manual review
Please contact the milestone owner if you have questions.
Owners: amineer@(Android), kariahda@(iOS), cindyb@(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Pls apply appropriate OSs label.

Added OS labels.

We consider r582121 to be safe, because it doesn't alter behaviour in a way visible to the user. It only changes the content of votes which are uploaded to the autofill server.

Approving merge for r582121 to M69 branch 3497 based on comment #5 and #9. Pls merge ASAP so we can pick it up for this week beta release. Thank you.

Approving merge for r582121 to M69 branch 3497 based on comment #5 and #9. Pls merge ASAP so we can pick it up for this week beta release. Thank you.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf

commit a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf
Author: Christos Froussios <cfroussios@chromium.org>
Date: Tue Aug 14 20:11:35 2018

[Password Manager] Split AUTOFILLED field flag

The flag currently indicates that the field was autofilled, regardless
of the trigger for autofilling.

We will now identify two triggers separately.
1. AUTOFILLED_ON_USER_TRIGGER. This refers to Fill On Account Select in
the context of the password manager. It also the current default
behaviour for Autofill.
2. AUTOFILLED_ON_PAGELOAD. Password manager determined that a password
form is a login form and filled the credentials as soon as the page was
loaded.

Any conditions which took AUTOFILLED into account are made to work with
either of the new flags.

TBR=cfroussios@chromium.org

(cherry picked from commit 1fdadcba612f7b1c5697fc82010f3df80e7da392)

Bug:  867348 
Change-Id: I2eb5fea7219ce784822174de24e76b3e1e4f1f15
Reviewed-on: https://chromium-review.googlesource.com/1169060
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Commit-Queue: Christos Froussios <cfroussios@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#582121}
Reviewed-on: https://chromium-review.googlesource.com/1174839
Reviewed-by: Christos Froussios <cfroussios@chromium.org>
Cr-Commit-Position: refs/branch-heads/3497@{#627}
Cr-Branched-From: 271eaf50594eb818c9295dc78d364aea18c82ea8-refs/heads/master@{#576753}
[modify] https://crrev.com/a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf/components/autofill/content/renderer/password_autofill_agent.cc
[modify] https://crrev.com/a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf/components/autofill/core/common/form_field_data.h
[modify] https://crrev.com/a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf/components/password_manager/core/browser/browser_save_password_progress_logger.cc
[modify] https://crrev.com/a21a3a1a2e92cc4c2b5d2fff2592c3d8c7ad08cf/components/password_manager/core/browser/form_parsing/form_parser_unittest.cc