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// Copyright 2025 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/metrics/fre_source_trial.h"
#include "base/feature_list.h"
#include "base/metrics/field_trial.h"
#include "base/strings/string_number_conversions.h"
#include "components/metrics/metrics_features.h"
#include "components/prefs/pref_registry_simple.h"
#include "components/prefs/pref_service.h"
#include "components/variations/variations_associated_data.h"
namespace metrics::fre_source_trial {
namespace {
scoped_refptr<base::FieldTrial> CreateFieldTrial(
const base::FieldTrial::EntropyProvider& entropy_provider) {
return base::FieldTrialList::FactoryGetFieldTrial(
kFRESourceTrial, /*total_probability=*/100, kDefaultGroup,
entropy_provider);
}
std::string CreateFirstRunTrial(
const base::FieldTrial::EntropyProvider& entropy_provider,
version_info::Channel channel) {
int enabled_percent = 0;
int control_percent = 0;
int default_percent = 100;
switch (channel) {
case version_info::Channel::CANARY:
case version_info::Channel::DEV:
case version_info::Channel::BETA:
enabled_percent = 50;
control_percent = 50;
default_percent = 0;
break;
default:
break;
}
// Set up the trial and groups.
scoped_refptr<base::FieldTrial> trial = CreateFieldTrial(entropy_provider);
trial->AppendGroup(kEnabledGroup, enabled_percent);
trial->AppendGroup(kControlGroup, control_percent);
trial->AppendGroup(kDefaultGroup, default_percent);
// Finalize the group choice. `group_name()` calls `Activate()` internally.
return trial->group_name();
}
void CreateSubsequentRunTrial(
const std::string& group_name,
const base::FieldTrial::EntropyProvider& entropy_provider) {
scoped_refptr<base::FieldTrial> trial = CreateFieldTrial(entropy_provider);
trial->AppendGroup(group_name, /*group_probability=*/100);
trial->Activate();
}
} // namespace
void RegisterLocalStatePrefs(PrefRegistrySimple* registry) {
registry->RegisterStringPref(kFRESourceTrial, "");
}
bool IsEnabled() {
return base::FieldTrialList::FindFullName(kFRESourceTrial) == kEnabledGroup;
}
void Create(PrefService* local_state,
const base::FieldTrial::EntropyProvider& entropy_provider,
version_info::Channel channel,
bool is_fre) {
CHECK(!base::FieldTrialList::TrialExists(kFRESourceTrial))
<< "Trial already exists.";
const std::string& trial_group = local_state->GetString(kFRESourceTrial);
if (is_fre && trial_group.empty()) {
const std::string new_trial_group =
CreateFirstRunTrial(entropy_provider, channel);
// Persist the assigned group for subsequent runs.
local_state->SetString(kFRESourceTrial, new_trial_group);
} else if (!trial_group.empty()) {
// Group already assigned in a previous run, so we assign it again.
CreateSubsequentRunTrial(trial_group, entropy_provider);
}
}
} // namespace metrics::fre_source_trial
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