chromium/components/page_load_metrics/browser/observers/use_counter/webdev_metrics_ukm_features.cc

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/page_load_metrics/browser/observers/use_counter_page_load_metrics_observer.h"

#include "base/no_destructor.h"

// This file defines a list of UseCounter WebFeature measured in the
// Web Developer Metric UKM UseCounter. Features must all satisfy UKM
// privacy requirements (see go/ukm). In addition, features should only be added
// if the expected frequency is less than 5% of page loads.
//
// The Web Developer Metrics UKM UseCounter is intended for features that are
// launching or may be subject to spec revisions. The UKM data is used to tie
// feature usage by a site to performance, devtools usage or other aspects of
// the site's structure. The event may also be used for investigations into
// features with unknown or unexpected UseCounter data in order to identify
// sites for further attention.
//
// Do NOT use this list for features that are being considered for removal or
// deprecation where percentage of page views or URLs is important. This event
// may be subsampled by the UKM system (some proportion of events may be dropped
// before being uploaded from the client) in order to balance the resources of
// the UKM system at large. As a result, any feature usage counts or
// percentages aggregated across all page views or URLs will be inaccurate.
// For such cases use the Blink.UseCounter allow list found in
// components/page_load_metrics/browser/observers/use_counter/ukm_features.cc.

WebFeature;

// UKM-based UseCounter features (WebFeature) should be defined in
// opt_in_features list.
const UseCounterMetricsRecorder::UkmFeatureList&
UseCounterMetricsRecorder::GetAllowedWebDevMetricsUkmFeatures() { … }