The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/522c2229aa8de418bb84be01b7386d3eb1d8ab65

commit 522c2229aa8de418bb84be01b7386d3eb1d8ab65
Author: Parastoo Geranmayeh <parastoog@google.com>
Date: Mon Jul 16 15:14:03 2018

[Autofill] Dynamic/Synthetic form refill.

Problem: Some forms have multiple fields for a single logical field,
only one of which is visible at a time. As the user is filling the form,
the visibility of the fields switches.
Case I: the user changes the country from US to CA, and the state
field changes from a select to text.
Case II: We have two fields, and both of them are detected as a certain
type. One is hidden and the other is visible at the time of filling the form.
Then as the autofill fills out the form, the visibility status of both fields
change, and it looks as if the entered value was removed by the website.
(See go/synthetic-fields section 2.2.)
Solution: After filling the form, get the form of the clicked on element
again, compare it with the old form, and if changed, trigger a refill.

Bug: 861877, 863428
Change-Id: I32515e37b5f9f092fd213f9538fdc9dda3933747
Reviewed-on: https://chromium-review.googlesource.com/1135199
Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Commit-Queue: Parastoo Geranmayeh <parastoog@google.com>
Cr-Commit-Position: refs/heads/master@{#575272}
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/chrome/browser/autofill/autofill_interactive_uitest.cc
[add] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/chrome/test/data/autofill/dynamic_form_select_to_text.html
[add] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/chrome/test/data/autofill/dynamic_form_visibility_switch.html
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/content/renderer/autofill_agent.cc
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/content/renderer/autofill_agent.h
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/core/common/form_data.cc
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/core/common/form_data.h
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/core/common/form_field_data.cc
[modify] https://crrev.com/522c2229aa8de418bb84be01b7386d3eb1d8ab65/components/autofill/core/common/form_field_data.h

To be fixed for iOS.

 Issue 835897  has been merged into this issue.