The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/55f20e1cb362685a9d632703758a3a69e9784f4b

commit 55f20e1cb362685a9d632703758a3a69e9784f4b
Author: Maxim Kolosovskiy <kolos@chromium.org>
Date: Tue Nov 21 09:26:41 2017

[Password Manager] Introduce UMA histogram for username detection method

Bug: 786404
Change-Id: Ib04d8064a16369b4daf162cb1deee4c98b44f398
Reviewed-on: https://chromium-review.googlesource.com/776668
Commit-Queue: Maxim Kolosovskiy <kolos@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Vadym Doroshenko <dvadym@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518192}
[modify] https://crrev.com/55f20e1cb362685a9d632703758a3a69e9784f4b/components/autofill/content/renderer/password_form_conversion_utils.cc
[modify] https://crrev.com/55f20e1cb362685a9d632703758a3a69e9784f4b/components/autofill/content/renderer/password_form_conversion_utils.h
[modify] https://crrev.com/55f20e1cb362685a9d632703758a3a69e9784f4b/components/autofill/content/renderer/password_form_conversion_utils_browsertest.cc
[modify] https://crrev.com/55f20e1cb362685a9d632703758a3a69e9784f4b/tools/metrics/histograms/enums.xml
[modify] https://crrev.com/55f20e1cb362685a9d632703758a3a69e9784f4b/tools/metrics/histograms/histograms.xml

The metric is implemented. I'll keep the bug open till we collect enough data.