The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e730ea4cc13580c7804737ebdbd6caa1e3b41270

commit e730ea4cc13580c7804737ebdbd6caa1e3b41270
Author: Yao Xiao <yaoxia@chromium.org>
Date: Wed Nov 07 23:57:54 2018

Add UseCounter for ad clicks on page

Besides, as a result of exploring different approaches, this CL additionally
adds FromAdState enum that can be potentially shared between WindowOpen and
other event. Made the testing logic easier to follow by switching
to parameter test and expecting single UMA/UKM entry per test.

Bug: 897256
Change-Id: Ic3f0e3637de77968f15e17f25d340d2456f988ef
Reviewed-on: https://chromium-review.googlesource.com/c/1292369
Commit-Queue: Yao Xiao <yaoxia@chromium.org>
Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606226}
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/chrome/browser/page_load_metrics/observers/use_counter/ukm_features.cc
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/chrome/browser/subresource_filter/ad_tagging_browsertest.cc
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/common/BUILD.gn
[add] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/common/frame/from_ad_state.cc
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/public/common/BUILD.gn
[add] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/public/common/frame/from_ad_state.h
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/public/platform/web_feature.mojom
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/renderer/core/dom/events/event_dispatcher.cc
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/third_party/blink/renderer/core/page/create_window.cc
[modify] https://crrev.com/e730ea4cc13580c7804737ebdbd6caa1e3b41270/tools/metrics/histograms/enums.xml