The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/39537d31826874aac9f1947a0421a27a948f6238

commit 39537d31826874aac9f1947a0421a27a948f6238
Author: Vadym Doroshenko <dvadym@chromium.org>
Date: Wed May 09 10:52:56 2018

Blink stable ids for forms and form control elements.

This CL implements UniqueRendererFormId and UniqueRendererFormControlId
methods in forms and form control elements correspondingly, which
return consecutive numbers of the current form and the form control
element in the current renderer process. Hence these ids are unique in
the same Renderer process modulo unsigned int overflow (which is not
the problem for Password Manager and Autofill).

Details go/blink-form-stable-ids

Bug:831119

Change-Id: Ie0c54363bc069b0f8953a3238ccd08262c7efd3c
Reviewed-on: https://chromium-review.googlesource.com/1002847
Commit-Queue: Vadym Doroshenko <dvadym@chromium.org>
Reviewed-by: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557141}
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/public/web/web_form_control_element.h
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/public/web/web_form_element.h
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/BUILD.gn
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/exported/web_form_control_element.cc
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/exported/web_form_element.cc
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_control_element.cc
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_control_element.h
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_control_element_test.cc
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_element.cc
[modify] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_element.h
[add] https://crrev.com/39537d31826874aac9f1947a0421a27a948f6238/third_party/blink/renderer/core/html/forms/html_form_element_test.cc