blob: a59c6148cf4ebdcfc817d63527b04af91972d1fd [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/prefs/pref_service.h"
#include <algorithm>
#include <map>
#include <utility>
#include "base/bind.h"
#include "base/debug/alias.h"
#include "base/debug/dump_without_crashing.h"
#include "base/files/file_path.h"
#include "base/location.h"
#include "base/logging.h"
#include "base/memory/ptr_util.h"
#include "base/metrics/histogram.h"
#include "base/single_thread_task_runner.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/threading/thread_task_runner_handle.h"
#include "base/util/values/values_util.h"
#include "base/value_conversions.h"
#include "build/build_config.h"
#include "components/prefs/default_pref_store.h"
#include "components/prefs/pref_notifier_impl.h"
#include "components/prefs/pref_registry.h"
namespace {
class ReadErrorHandler : public PersistentPrefStore::ReadErrorDelegate {
public:
using ErrorCallback =
base::RepeatingCallback<void(PersistentPrefStore::PrefReadError)>;
explicit ReadErrorHandler(ErrorCallback cb) : callback_(cb) {}
void OnError(PersistentPrefStore::PrefReadError error) override {
callback_.Run(error);
}
private:
ErrorCallback callback_;
DISALLOW_COPY_AND_ASSIGN(ReadErrorHandler);
};
// Returns the WriteablePrefStore::PrefWriteFlags for the pref with the given
// |path|.
uint32_t GetWriteFlags(const PrefService::Preference* pref) {
uint32_t write_flags = WriteablePrefStore::DEFAULT_PREF_WRITE_FLAGS;
if (!pref)
return write_flags;
if (pref->registration_flags() & PrefRegistry::LOSSY_PREF)
write_flags |= WriteablePrefStore::LOSSY_PREF_WRITE_FLAG;
return write_flags;
}
// For prefs names in |pref_store| that are not presented in |pref_changed_map|,
// check if their values differ from those in pref_service->FindPreference() and
// add the result into |pref_changed_map|.
void CheckForNewPrefChangesInPrefStore(
std::map<std::string, bool>* pref_changed_map,
PrefStore* pref_store,
PrefService* pref_service) {
if (!pref_store)
return;
auto values = pref_store->GetValues();
for (const auto& item : values->DictItems()) {
// If the key already presents, skip it as a store with higher precedence
// already sets the entry.
if (pref_changed_map->find(item.first) != pref_changed_map->end())
continue;
const PrefService::Preference* pref =
pref_service->FindPreference(item.first);
if (!pref)
continue;
pref_changed_map->emplace(item.first, *(pref->GetValue()) != item.second);
}
}
} // namespace
PrefService::PrefService(
std::unique_ptr<PrefNotifierImpl> pref_notifier,
std::unique_ptr<PrefValueStore> pref_value_store,
scoped_refptr<PersistentPrefStore> user_prefs,
scoped_refptr<PrefRegistry> pref_registry,
base::RepeatingCallback<void(PersistentPrefStore::PrefReadError)>
read_error_callback,
bool async)
: pref_notifier_(std::move(pref_notifier)),
pref_value_store_(std::move(pref_value_store)),
user_pref_store_(std::move(user_prefs)),
read_error_callback_(std::move(read_error_callback)),
pref_registry_(std::move(pref_registry)) {
#if defined(STARBOARD)
LOG(INFO) << "PrefService::PrefService";
#endif
pref_notifier_->SetPrefService(this);
DCHECK(pref_registry_);
DCHECK(pref_value_store_);
InitFromStorage(async);
}
PrefService::~PrefService() {
#if defined(STARBOARD)
LOG(INFO) << "PrefService::~PrefService";
#endif
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
// TODO(crbug.com/942491, 946668, 945772) The following code collects
// augments stack dumps created by ~PrefNotifierImpl() with information
// whether the profile owning the PrefService is an incognito profile.
// Delete this, once the bugs are closed.
const bool is_incognito_profile = user_pref_store_->IsInMemoryPrefStore();
base::debug::Alias(&is_incognito_profile);
// Export value of is_incognito_profile to a string so that `grep`
// is a sufficient tool to analyze crashdumps.
char is_incognito_profile_string[32];
base::strlcpy(is_incognito_profile_string,
is_incognito_profile ? "is_incognito: yes" : "is_incognito: no",
sizeof(is_incognito_profile_string));
base::debug::Alias(&is_incognito_profile_string);
}
void PrefService::InitFromStorage(bool async) {
if (user_pref_store_->IsInitializationComplete()) {
read_error_callback_.Run(user_pref_store_->GetReadError());
} else if (!async) {
read_error_callback_.Run(user_pref_store_->ReadPrefs());
} else {
// Guarantee that initialization happens after this function returned.
base::ThreadTaskRunnerHandle::Get()->PostTask(
FROM_HERE,
base::BindOnce(&PersistentPrefStore::ReadPrefsAsync, user_pref_store_,
new ReadErrorHandler(read_error_callback_)));
}
}
void PrefService::CommitPendingWrite(
base::OnceClosure reply_callback,
base::OnceClosure synchronous_done_callback) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
user_pref_store_->CommitPendingWrite(std::move(reply_callback),
std::move(synchronous_done_callback));
}
void PrefService::SchedulePendingLossyWrites() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
user_pref_store_->SchedulePendingLossyWrites();
}
bool PrefService::GetBoolean(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
bool result = false;
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return result;
bool rv = value->GetAsBoolean(&result);
DCHECK(rv);
return result;
}
int PrefService::GetInteger(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
int result = 0;
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return result;
bool rv = value->GetAsInteger(&result);
DCHECK(rv);
return result;
}
double PrefService::GetDouble(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
double result = 0.0;
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return result;
bool rv = value->GetAsDouble(&result);
DCHECK(rv);
return result;
}
std::string PrefService::GetString(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
std::string result;
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return result;
bool rv = value->GetAsString(&result);
DCHECK(rv);
return result;
}
base::FilePath PrefService::GetFilePath(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
base::FilePath result;
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return base::FilePath(result);
bool rv = base::GetValueAsFilePath(*value, &result);
DCHECK(rv);
return result;
}
bool PrefService::HasPrefPath(const std::string& path) const {
const Preference* pref = FindPreference(path);
return pref && !pref->IsDefaultValue();
}
void PrefService::IteratePreferenceValues(
base::RepeatingCallback<void(const std::string& key,
const base::Value& value)> callback) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
for (const auto& it : *pref_registry_)
callback.Run(it.first, *GetPreferenceValue(it.first));
}
std::unique_ptr<base::DictionaryValue> PrefService::GetPreferenceValues(
IncludeDefaults include_defaults) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
std::unique_ptr<base::DictionaryValue> out(new base::DictionaryValue);
for (const auto& it : *pref_registry_) {
if (include_defaults == INCLUDE_DEFAULTS) {
out->Set(it.first, GetPreferenceValue(it.first)->CreateDeepCopy());
} else {
const Preference* pref = FindPreference(it.first);
if (pref->IsDefaultValue())
continue;
out->Set(it.first, pref->GetValue()->CreateDeepCopy());
}
}
return out;
}
const PrefService::Preference* PrefService::FindPreference(
const std::string& pref_name) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
auto it = prefs_map_.find(pref_name);
if (it != prefs_map_.end())
return &(it->second);
const base::Value* default_value = nullptr;
if (!pref_registry_->defaults()->GetValue(pref_name, &default_value))
return nullptr;
it = prefs_map_
.insert(std::make_pair(
pref_name, Preference(this, pref_name, default_value->type())))
.first;
return &(it->second);
}
bool PrefService::ReadOnly() const {
return user_pref_store_->ReadOnly();
}
PrefService::PrefInitializationStatus PrefService::GetInitializationStatus()
const {
if (!user_pref_store_->IsInitializationComplete())
return INITIALIZATION_STATUS_WAITING;
switch (user_pref_store_->GetReadError()) {
case PersistentPrefStore::PREF_READ_ERROR_NONE:
return INITIALIZATION_STATUS_SUCCESS;
case PersistentPrefStore::PREF_READ_ERROR_NO_FILE:
return INITIALIZATION_STATUS_CREATED_NEW_PREF_STORE;
default:
return INITIALIZATION_STATUS_ERROR;
}
}
PrefService::PrefInitializationStatus
PrefService::GetAllPrefStoresInitializationStatus() const {
if (!pref_value_store_->IsInitializationComplete())
return INITIALIZATION_STATUS_WAITING;
return GetInitializationStatus();
}
bool PrefService::IsManagedPreference(const std::string& pref_name) const {
const Preference* pref = FindPreference(pref_name);
return pref && pref->IsManaged();
}
bool PrefService::IsPreferenceManagedByCustodian(
const std::string& pref_name) const {
const Preference* pref = FindPreference(pref_name);
return pref && pref->IsManagedByCustodian();
}
bool PrefService::IsUserModifiablePreference(
const std::string& pref_name) const {
const Preference* pref = FindPreference(pref_name);
return pref && pref->IsUserModifiable();
}
const base::Value* PrefService::Get(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return nullptr;
return value;
}
const base::DictionaryValue* PrefService::GetDictionary(
const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return nullptr;
if (value->type() != base::Value::Type::DICTIONARY) {
NOTREACHED();
return nullptr;
}
return static_cast<const base::DictionaryValue*>(value);
}
const base::Value* PrefService::GetUserPrefValue(
const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const Preference* pref = FindPreference(path);
if (!pref) {
NOTREACHED() << "Trying to get an unregistered pref: " << path;
return nullptr;
}
// Look for an existing preference in the user store. If it doesn't
// exist, return NULL.
base::Value* value = nullptr;
if (!user_pref_store_->GetMutableValue(path, &value))
return nullptr;
if (value->type() != pref->GetType()) {
NOTREACHED() << "Pref value type doesn't match registered type.";
return nullptr;
}
return value;
}
void PrefService::SetDefaultPrefValue(const std::string& path,
base::Value value) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
pref_registry_->SetDefaultPrefValue(path, std::move(value));
}
const base::Value* PrefService::GetDefaultPrefValue(
const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
// Lookup the preference in the default store.
const base::Value* value = nullptr;
bool has_value = pref_registry_->defaults()->GetValue(path, &value);
DCHECK(has_value) << "Default value missing for pref: " << path;
return value;
}
const base::ListValue* PrefService::GetList(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return nullptr;
if (value->type() != base::Value::Type::LIST) {
NOTREACHED();
return nullptr;
}
return static_cast<const base::ListValue*>(value);
}
void PrefService::AddPrefObserver(const std::string& path, PrefObserver* obs) {
pref_notifier_->AddPrefObserver(path, obs);
}
void PrefService::RemovePrefObserver(const std::string& path,
PrefObserver* obs) {
pref_notifier_->RemovePrefObserver(path, obs);
}
void PrefService::AddPrefInitObserver(base::OnceCallback<void(bool)> obs) {
pref_notifier_->AddInitObserver(std::move(obs));
}
PrefRegistry* PrefService::DeprecatedGetPrefRegistry() {
return pref_registry_.get();
}
void PrefService::ClearPref(const std::string& path) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const Preference* pref = FindPreference(path);
if (!pref) {
NOTREACHED() << "Trying to clear an unregistered pref: " << path;
return;
}
user_pref_store_->RemoveValue(path, GetWriteFlags(pref));
}
void PrefService::ClearMutableValues() {
user_pref_store_->ClearMutableValues();
}
void PrefService::OnStoreDeletionFromDisk() {
user_pref_store_->OnStoreDeletionFromDisk();
}
void PrefService::ChangePrefValueStore(
PrefStore* managed_prefs,
PrefStore* supervised_user_prefs,
PrefStore* extension_prefs,
PrefStore* recommended_prefs,
std::unique_ptr<PrefValueStore::Delegate> delegate) {
// Only adding new pref stores are supported.
DCHECK(!pref_value_store_->HasPrefStore(PrefValueStore::MANAGED_STORE) ||
!managed_prefs);
DCHECK(
!pref_value_store_->HasPrefStore(PrefValueStore::SUPERVISED_USER_STORE) ||
!supervised_user_prefs);
DCHECK(!pref_value_store_->HasPrefStore(PrefValueStore::EXTENSION_STORE) ||
!extension_prefs);
DCHECK(!pref_value_store_->HasPrefStore(PrefValueStore::RECOMMENDED_STORE) ||
!recommended_prefs);
// If some of the stores are already initialized, check for pref value changes
// according to store precedence.
std::map<std::string, bool> pref_changed_map;
CheckForNewPrefChangesInPrefStore(&pref_changed_map, managed_prefs, this);
CheckForNewPrefChangesInPrefStore(&pref_changed_map, supervised_user_prefs,
this);
CheckForNewPrefChangesInPrefStore(&pref_changed_map, extension_prefs, this);
CheckForNewPrefChangesInPrefStore(&pref_changed_map, recommended_prefs, this);
pref_value_store_ = pref_value_store_->CloneAndSpecialize(
managed_prefs, supervised_user_prefs, extension_prefs,
nullptr /* command_line_prefs */, nullptr /* user_prefs */,
recommended_prefs, nullptr /* default_prefs */, pref_notifier_.get(),
std::move(delegate));
// Notify |pref_notifier_| on all changed values.
for (const auto& kv : pref_changed_map) {
if (kv.second)
pref_notifier_.get()->OnPreferenceChanged(kv.first);
}
}
void PrefService::AddPrefObserverAllPrefs(PrefObserver* obs) {
pref_notifier_->AddPrefObserverAllPrefs(obs);
}
void PrefService::RemovePrefObserverAllPrefs(PrefObserver* obs) {
pref_notifier_->RemovePrefObserverAllPrefs(obs);
}
void PrefService::Set(const std::string& path, const base::Value& value) {
SetUserPrefValue(path, value.CreateDeepCopy());
}
void PrefService::SetBoolean(const std::string& path, bool value) {
SetUserPrefValue(path, std::make_unique<base::Value>(value));
}
void PrefService::SetInteger(const std::string& path, int value) {
SetUserPrefValue(path, std::make_unique<base::Value>(value));
}
void PrefService::SetDouble(const std::string& path, double value) {
SetUserPrefValue(path, std::make_unique<base::Value>(value));
}
void PrefService::SetString(const std::string& path, const std::string& value) {
SetUserPrefValue(path, std::make_unique<base::Value>(value));
}
void PrefService::SetFilePath(const std::string& path,
const base::FilePath& value) {
SetUserPrefValue(
path, base::Value::ToUniquePtrValue(base::CreateFilePathValue(value)));
}
void PrefService::SetInt64(const std::string& path, int64_t value) {
SetUserPrefValue(path,
base::Value::ToUniquePtrValue(util::Int64ToValue(value)));
}
int64_t PrefService::GetInt64(const std::string& path) const {
const base::Value* value = GetPreferenceValueChecked(path);
base::Optional<int64_t> integer = util::ValueToInt64(value);
DCHECK(integer);
return integer.value_or(0);
}
void PrefService::SetUint64(const std::string& path, uint64_t value) {
SetUserPrefValue(path,
std::make_unique<base::Value>(base::NumberToString(value)));
}
uint64_t PrefService::GetUint64(const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const base::Value* value = GetPreferenceValueChecked(path);
if (!value)
return 0;
std::string result("0");
bool rv = value->GetAsString(&result);
DCHECK(rv);
uint64_t val;
base::StringToUint64(result, &val);
return val;
}
void PrefService::SetTime(const std::string& path, base::Time value) {
SetUserPrefValue(path,
base::Value::ToUniquePtrValue(util::TimeToValue(value)));
}
base::Time PrefService::GetTime(const std::string& path) const {
const base::Value* value = GetPreferenceValueChecked(path);
base::Optional<base::Time> time = util::ValueToTime(value);
DCHECK(time);
return time.value_or(base::Time());
}
void PrefService::SetTimeDelta(const std::string& path, base::TimeDelta value) {
SetUserPrefValue(
path, base::Value::ToUniquePtrValue(util::TimeDeltaToValue(value)));
}
base::TimeDelta PrefService::GetTimeDelta(const std::string& path) const {
const base::Value* value = GetPreferenceValueChecked(path);
base::Optional<base::TimeDelta> time_delta = util::ValueToTimeDelta(value);
DCHECK(time_delta);
return time_delta.value_or(base::TimeDelta());
}
base::Value* PrefService::GetMutableUserPref(const std::string& path,
base::Value::Type type) {
CHECK(type == base::Value::Type::DICTIONARY ||
type == base::Value::Type::LIST);
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const Preference* pref = FindPreference(path);
if (!pref) {
NOTREACHED() << "Trying to get an unregistered pref: " << path;
return nullptr;
}
if (pref->GetType() != type) {
NOTREACHED() << "Wrong type for GetMutableValue: " << path;
return nullptr;
}
// Look for an existing preference in the user store. Return it in case it
// exists and has the correct type.
base::Value* value = nullptr;
if (user_pref_store_->GetMutableValue(path, &value) &&
value->type() == type) {
return value;
}
// TODO(crbug.com/859477): Remove once root cause has been found.
if (value && value->type() != type) {
DEBUG_ALIAS_FOR_CSTR(path_copy, path.c_str(), 1024);
base::debug::DumpWithoutCrashing();
}
// If no user preference of the correct type exists, clone default value.
const base::Value* default_value = nullptr;
pref_registry_->defaults()->GetValue(path, &default_value);
// TODO(crbug.com/859477): Revert to DCHECK once root cause has been found.
if (default_value->type() != type) {
DEBUG_ALIAS_FOR_CSTR(path_copy, path.c_str(), 1024);
base::debug::DumpWithoutCrashing();
}
user_pref_store_->SetValueSilently(path, default_value->CreateDeepCopy(),
GetWriteFlags(pref));
user_pref_store_->GetMutableValue(path, &value);
return value;
}
void PrefService::ReportUserPrefChanged(const std::string& key) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
user_pref_store_->ReportValueChanged(key, GetWriteFlags(FindPreference(key)));
}
void PrefService::ReportUserPrefChanged(
const std::string& key,
std::set<std::vector<std::string>> path_components) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
user_pref_store_->ReportSubValuesChanged(key, std::move(path_components),
GetWriteFlags(FindPreference(key)));
}
void PrefService::SetUserPrefValue(const std::string& path,
std::unique_ptr<base::Value> new_value) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
const Preference* pref = FindPreference(path);
if (!pref) {
NOTREACHED() << "Trying to write an unregistered pref: " << path;
return;
}
if (pref->GetType() != new_value->type()) {
NOTREACHED() << "Trying to set pref " << path << " of type "
<< pref->GetType() << " to value of type "
<< new_value->type();
return;
}
user_pref_store_->SetValue(path, std::move(new_value), GetWriteFlags(pref));
}
void PrefService::UpdateCommandLinePrefStore(PrefStore* command_line_store) {
pref_value_store_->UpdateCommandLinePrefStore(command_line_store);
}
///////////////////////////////////////////////////////////////////////////////
// PrefService::Preference
PrefService::Preference::Preference(const PrefService* service,
std::string name,
base::Value::Type type)
: name_(std::move(name)),
type_(type),
// Cache the registration flags at creation time to avoid multiple map
// lookups later.
registration_flags_(service->pref_registry_->GetRegistrationFlags(name_)),
pref_service_(service) {}
const base::Value* PrefService::Preference::GetValue() const {
return pref_service_->GetPreferenceValueChecked(name_);
}
const base::Value* PrefService::Preference::GetRecommendedValue() const {
DCHECK(pref_service_->FindPreference(name_))
<< "Must register pref before getting its value";
const base::Value* found_value = nullptr;
if (pref_value_store()->GetRecommendedValue(name_, type_, &found_value)) {
DCHECK(found_value->type() == type_);
return found_value;
}
// The pref has no recommended value.
return nullptr;
}
bool PrefService::Preference::IsManaged() const {
return pref_value_store()->PrefValueInManagedStore(name_);
}
bool PrefService::Preference::IsManagedByCustodian() const {
return pref_value_store()->PrefValueInSupervisedStore(name_);
}
bool PrefService::Preference::IsRecommended() const {
return pref_value_store()->PrefValueFromRecommendedStore(name_);
}
bool PrefService::Preference::HasExtensionSetting() const {
return pref_value_store()->PrefValueInExtensionStore(name_);
}
bool PrefService::Preference::HasUserSetting() const {
return pref_value_store()->PrefValueInUserStore(name_);
}
bool PrefService::Preference::IsExtensionControlled() const {
return pref_value_store()->PrefValueFromExtensionStore(name_);
}
bool PrefService::Preference::IsUserControlled() const {
return pref_value_store()->PrefValueFromUserStore(name_);
}
bool PrefService::Preference::IsDefaultValue() const {
return pref_value_store()->PrefValueFromDefaultStore(name_);
}
bool PrefService::Preference::IsUserModifiable() const {
return pref_value_store()->PrefValueUserModifiable(name_);
}
bool PrefService::Preference::IsExtensionModifiable() const {
return pref_value_store()->PrefValueExtensionModifiable(name_);
}
const base::Value* PrefService::GetPreferenceValue(
const std::string& path) const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
// TODO(battre): This is a check for crbug.com/435208. After analyzing some
// crash dumps it looks like the PrefService is accessed even though it has
// been cleared already.
CHECK(pref_registry_);
CHECK(pref_registry_->defaults());
CHECK(pref_value_store_);
const base::Value* default_value = nullptr;
if (pref_registry_->defaults()->GetValue(path, &default_value)) {
const base::Value* found_value = nullptr;
base::Value::Type default_type = default_value->type();
if (pref_value_store_->GetValue(path, default_type, &found_value)) {
DCHECK(found_value->type() == default_type);
return found_value;
} else {
// Every registered preference has at least a default value.
NOTREACHED() << "no valid value found for registered pref " << path;
}
}
return nullptr;
}
const base::Value* PrefService::GetPreferenceValueChecked(
const std::string& path) const {
const base::Value* value = GetPreferenceValue(path);
DCHECK(value) << "Trying to read an unregistered pref: " << path;
return value;
}