battre@chromium.org, nepper@chromium.org: FYI just in case you want to track this.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1695afd6c7d1c7370f3cf995e28af60ad71d4c49

commit 1695afd6c7d1c7370f3cf995e28af60ad71d4c49
Author: Maxim Kolosovskiy <kolos@chromium.org>
Date: Wed Jun 13 10:50:50 2018

[Password Generation] Some changes of password generation metrics

- introduces the metric of whether manual or automatic generation was triggered
- fixes a bug in reporting NO_SIGN_UP_DETECTED and SIGN_UP_DETECTED
- disables reporting of PasswordGenerationEvent if generation is disabled

Bug:  851401 
Change-Id: I4ccd4bfb5847d108a671571601e85fbf876de637
Reviewed-on: https://chromium-review.googlesource.com/1095177
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Commit-Queue: Maxim Kolosovskiy <kolos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566794}
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/autofill/content/renderer/password_generation_agent.cc
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/autofill/content/renderer/password_generation_agent.h
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/autofill/core/common/password_generation_util.h
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/password_manager/core/browser/password_form_manager.cc
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/password_manager/core/browser/password_form_manager_unittest.cc
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/components/password_manager/core/browser/votes_uploader.cc
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/1695afd6c7d1c7370f3cf995e28af60ad71d4c49/tools/metrics/histograms/histograms.xml