chromecast/base/cast_features.cc - chromium/src - Git at Google

 // Copyright 2017 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 "chromecast/base/cast_features.h"

 #include <algorithm>
 #include <utility>

 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/field_trial_param_associator.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/no_destructor.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/values.h"
 #include "build/build_config.h"

 namespace chromecast {
 namespace {
 // A constant used to always activate a FieldTrial.
 const base::FieldTrial::Probability k100PercentProbability = 100;

 // The name of the default group to use for Cast DCS features.
 const char kDefaultDCSFeaturesGroup[] = "default_dcs_features_group";

 std::unordered_set<int32_t>& GetExperimentIds() {
   static base::NoDestructor<std::unordered_set<int32_t>> g_experiment_ids;
   return *g_experiment_ids;
 }

 bool g_experiment_ids_initialized = false;

 // The collection of features that have been registered by unit tests
 std::vector<const base::Feature*>& GetTestFeatures() {
   static base::NoDestructor<std::vector<const base::Feature*>>
       features_for_test;
   return *features_for_test;
 }

 void SetExperimentIds(const base::ListValue& list) {
   DCHECK(!g_experiment_ids_initialized);
   std::unordered_set<int32_t> ids;
   for (size_t i = 0; i < list.GetSize(); ++i) {
     int32_t id;
     if (list.GetInteger(i, &id)) {
       ids.insert(id);
     } else {
       LOG(ERROR) << "Non-integer value found in experiment id list!";
     }
   }
   GetExperimentIds().swap(ids);
   g_experiment_ids_initialized = true;
 }

 }  // namespace

 // PLEASE READ!
 // Cast Platform Features are listed below. These features may be
 // toggled via configs fetched from DCS for devices in the field, or via
 // command-line flags set by the developer. For the end-to-end details of the
 // system design, please see go/dcs-experiments.
 //
 // Below are useful steps on how to use these features in your code.
 //
 // 1) Declaring and defining the feature.
 //    All Cast Platform Features should be declared in a common file with other
 //    Cast Platform Features (ex. chromecast/base/cast_features.h). When
 //    defining your feature, you will need to assign a default value. This is
 //    the value that the feature will hold until overriden by the server or the
 //    command line. Here's an exmaple:
 //
 //      const base::Feature kSuperSecretSauce{
 //          "enable_super_secret_sauce", base::FEATURE_DISABLED_BY_DEFAULT};
 //
 //    IMPORTANT NOTE:
 //    The first parameter that you pass in the definition is the feature's name.
 //    This MUST match the DCS experiment key for this feature.
 //
 //    While Features elsewhere in Chromium alternatively use dashed-case or
 //    PascalCase for their names, Chromecast features should use snake_case
 //    (lowercase letters separated by underscores). This will ensure that DCS
 //    configs, which are passed around as JSON, remain conformant and readable.
 //
 // 2) Using the feature in client code.
 //    Using these features in your code is easy. Here's an example:
 //
 //      #include “base/feature_list.h”
 //      #include “chromecast/base/chromecast_switches.h”
 //
 //      std::unique_ptr<Foo> CreateFoo() {
 //        if (base::FeatureList::IsEnabled(kSuperSecretSauce))
 //          return std::make_unique<SuperSecretFoo>();
 //        return std::make_unique<BoringOldFoo>();
 //      }
 //
 //    base::FeatureList can be called from any thread, in any process, at any
 //    time after PreCreateThreads(). It will return whether the feature is
 //    enabled.
 //
 // 3) Overriding the default value from the server.
 //    For devices in the field, DCS will issue different configs to different
 //    groups of devices, allowing us to run experiments on features. These
 //    feature settings will manifest on the next boot of cast_shell. In the
 //    example, if the latest config for a particular device set the value of
 //    kSuperSecretSauce to true, the appropriate code path would be taken.
 //    Otherwise, the default value, false, would be used. For more details on
 //    setting up experiments, see go/dcs-launch.
 //
 // 4) Overriding the default and server values from the command-line.
 //    While the server value trumps the default values, the command line trumps
 //    both. Enable features by passing this command line arg to cast_shell:
 //
 //      --enable-features=enable_foo,enable_super_secret_sauce
 //
 //    Features are separated by commas. Disable features by passing:
 //
 //      --disable-features=enable_foo,enable_bar
 //
 // 5) If you add a new feature to the system you must include it in kFeatures
 //    This is because the system relies on knowing all of the features so
 //    it can properly iterate over all features to detect changes.
 //

 // Begin Chromecast Feature definitions.

 // Allows applications to access media capture devices (webcams/microphones)
 // through getUserMedia API.
 const base::Feature kAllowUserMediaAccess{"allow_user_media_access",
                                           base::FEATURE_DISABLED_BY_DEFAULT};
 // Enables the use of QUIC in Cast-specific URLRequestContextGetters. See
 // chromecast/browser/url_request_context_factory.cc for usage.
 const base::Feature kEnableQuic{"enable_quic",
                                 base::FEATURE_DISABLED_BY_DEFAULT};
 // Enables triple-buffer 720p graphics (overriding default graphics buffer
 // settings for a platform).
 const base::Feature kTripleBuffer720{"enable_triple_buffer_720",
                                      base::FEATURE_DISABLED_BY_DEFAULT};
 // Enables single-buffered graphics (overriding default graphics buffer
 // settings and takes precedence over triple-buffer feature).
 const base::Feature kSingleBuffer{"enable_single_buffer",
                                   base::FEATURE_DISABLED_BY_DEFAULT};
 // Disable idle sockets closing on memory pressure. See
 // chromecast/browser/url_request_context_factory.cc for usage.
 const base::Feature kDisableIdleSocketsCloseOnMemoryPressure{
     "disable_idle_sockets_close_on_memory_pressure",
     base::FEATURE_DISABLED_BY_DEFAULT};

 // End Chromecast Feature definitions.
 const base::Feature* kFeatures[] = {
     &kAllowUserMediaAccess,
     &kEnableQuic,
     &kTripleBuffer720,
     &kSingleBuffer,
     &kDisableIdleSocketsCloseOnMemoryPressure,
 };

 // An iterator for a base::DictionaryValue. Use an alias for brevity in loops.
 using Iterator = base::DictionaryValue::Iterator;

 std::vector<const base::Feature*> GetInternalFeatures();

 const std::vector<const base::Feature*>& GetFeatures() {
   static const base::NoDestructor<std::vector<const base::Feature*>> features(
       [] {
         auto features = std::vector<const base::Feature*>(
             kFeatures, kFeatures + sizeof(kFeatures) / sizeof(base::Feature*));
         auto internal_features = GetInternalFeatures();
         features.insert(features.end(), internal_features.begin(),
                         internal_features.end());
         return features;
       }());
   if (GetTestFeatures().size() > 0)
     return GetTestFeatures();
   return *features;
 }

 void InitializeFeatureList(const base::DictionaryValue& dcs_features,
                            const base::ListValue& dcs_experiment_ids,
                            const std::string& cmd_line_enable_features,
                            const std::string& cmd_line_disable_features,
                            const std::string& extra_enable_features,
                            const std::string& extra_disable_features) {
   DCHECK(!base::FeatureList::GetInstance());

   // Set the experiments.
   SetExperimentIds(dcs_experiment_ids);

   std::string all_enable_features =
       cmd_line_enable_features + "," + extra_enable_features;
   std::string all_disable_features =
       cmd_line_disable_features + "," + extra_disable_features;

   // Initialize the FeatureList from the command line.
   auto feature_list = std::make_unique<base::FeatureList>();
   feature_list->InitializeFromCommandLine(all_enable_features,
                                           all_disable_features);

   // Override defaults from the DCS config.
   for (Iterator it(dcs_features); !it.IsAtEnd(); it.Advance()) {
     // Each feature must have its own FieldTrial object. Since experiments are
     // controlled server-side for Chromecast, and this class is designed with a
     // client-side experimentation framework in mind, these parameters are
     // carefully chosen:
     //   - The field trial name is unused for our purposes. However, we need to
     //     maintain a 1:1 mapping with Features in order to properly store and
     //     access parameters associated with each Feature. Therefore, use the
     //     Feature's name as the FieldTrial name to ensure uniqueness.
     //   - The probability is hard-coded to 100% so that the FeatureList always
     //     respects the value from DCS.
     //   - The default group is unused; it will be the same for every feature.
     //   - Expiration year, month, and day use a special value such that the
     //     feature will never expire.
     //   - SESSION_RANDOMIZED is used to prevent the need for an
     //     entropy_provider. However, this value doesn't matter.
     //   - We don't care about the group_id.
     //
     const std::string& feature_name = it.key();
     auto* field_trial = base::FieldTrialList::FactoryGetFieldTrial(
         feature_name, k100PercentProbability, kDefaultDCSFeaturesGroup,
         base::FieldTrialList::kNoExpirationYear, 1 /* month */, 1 /* day */,
         base::FieldTrial::SESSION_RANDOMIZED, nullptr);

     bool enabled;
     if (it.value().GetAsBoolean(&enabled)) {
       // A boolean entry simply either enables or disables a feature.
       feature_list->RegisterFieldTrialOverride(
           feature_name,
           enabled ? base::FeatureList::OVERRIDE_ENABLE_FEATURE
                   : base::FeatureList::OVERRIDE_DISABLE_FEATURE,
           field_trial);
       continue;
     }

     const base::DictionaryValue* params_dict;
     if (it.value().GetAsDictionary(&params_dict)) {
       // A dictionary entry implies that the feature is enabled.
       feature_list->RegisterFieldTrialOverride(
           feature_name, base::FeatureList::OVERRIDE_ENABLE_FEATURE,
           field_trial);

       // If the feature has not been overriden from the command line, set its
       // parameters accordingly.
       if (!feature_list->IsFeatureOverriddenFromCommandLine(
               feature_name, base::FeatureList::OVERRIDE_DISABLE_FEATURE)) {
         // Build a map of the FieldTrial parameters and associate it to the
         // FieldTrial.
         base::FieldTrialParamAssociator::FieldTrialParams params;
         for (Iterator p(*params_dict); !p.IsAtEnd(); p.Advance()) {
           std::string val;
           if (p.value().GetAsString(&val)) {
             params[p.key()] = val;
           } else {
             LOG(ERROR) << "Entry in params dict for \"" << feature_name << "\""
                        << " feature is not a string. Skipping.";
           }
         }

         // Register the params, so that they can be queried by client code.
         bool success = base::AssociateFieldTrialParams(
             feature_name, kDefaultDCSFeaturesGroup, params);
         DCHECK(success);
       }
       continue;
     }

     // Other base::Value types are not supported.
     LOG(ERROR) << "A DCS feature mapped to an unsupported value. key: "
                << feature_name << " type: " << it.value().type();
   }

   base::FeatureList::SetInstance(std::move(feature_list));
 }

 bool IsFeatureEnabled(const base::Feature& feature) {
   DCHECK(base::ContainsValue(GetFeatures(), &feature)) << feature.name;
   return base::FeatureList::IsEnabled(feature);
 }

 base::DictionaryValue GetOverriddenFeaturesForStorage(
     const base::Value& features) {
   base::DictionaryValue persistent_dict;

   // |features| maps feature names to either a boolean or a dict of params.
   for (const auto& feature : features.DictItems()) {
     if (feature.second.is_bool()) {
       persistent_dict.SetBoolean(feature.first, feature.second.GetBool());
       continue;
     }

     const base::DictionaryValue* params_dict;
     if (feature.second.GetAsDictionary(&params_dict)) {
       auto params = std::make_unique<base::DictionaryValue>();

       bool bval;
       int ival;
       double dval;
       std::string sval;
       for (Iterator p(*params_dict); !p.IsAtEnd(); p.Advance()) {
         const auto& param_key = p.key();
         const auto& param_val = p.value();
         if (param_val.GetAsBoolean(&bval)) {
           params->SetString(param_key, bval ? "true" : "false");
         } else if (param_val.GetAsInteger(&ival)) {
           params->SetString(param_key, base::IntToString(ival));
         } else if (param_val.GetAsDouble(&dval)) {
           params->SetString(param_key, base::NumberToString(dval));
         } else if (param_val.GetAsString(&sval)) {
           params->SetString(param_key, sval);
         } else {
           LOG(ERROR) << "Entry in params dict for \"" << feature.first << "\""
                      << " is not of a supported type (key: " << param_key
                      << ", type: " << param_val.type();
         }
       }
       persistent_dict.Set(feature.first, std::move(params));
       continue;
     }

     // Other base::Value types are not supported.
     LOG(ERROR) << "A DCS feature mapped to an unsupported value. key: "
                << feature.first << " type: " << feature.second.type();
   }

   return persistent_dict;
 }

 const std::unordered_set<int32_t>& GetDCSExperimentIds() {
   DCHECK(g_experiment_ids_initialized);
   return GetExperimentIds();
 }

 void ResetCastFeaturesForTesting() {
   g_experiment_ids_initialized = false;
   base::FeatureList::ClearInstanceForTesting();
   GetTestFeatures().clear();
 }

 void SetFeaturesForTest(std::vector<const base::Feature*> features) {
   GetTestFeatures() = std::move(features);
 }

 }  // namespace chromecast
	// Copyright 2017 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 "chromecast/base/cast_features.h"

	#include <algorithm>
	#include <utility>

	#include "base/command_line.h"
	#include "base/feature_list.h"
	#include "base/metrics/field_trial.h"
	#include "base/metrics/field_trial_param_associator.h"
	#include "base/metrics/field_trial_params.h"
	#include "base/no_destructor.h"
	#include "base/stl_util.h"
	#include "base/strings/string_number_conversions.h"
	#include "base/values.h"
	#include "build/build_config.h"

	namespace chromecast {
	namespace {
	// A constant used to always activate a FieldTrial.
	const base::FieldTrial::Probability k100PercentProbability = 100;

	// The name of the default group to use for Cast DCS features.
	const char kDefaultDCSFeaturesGroup[] = "default_dcs_features_group";

	std::unordered_set<int32_t>& GetExperimentIds() {
	static base::NoDestructor<std::unordered_set<int32_t>> g_experiment_ids;
	return *g_experiment_ids;
	}

	bool g_experiment_ids_initialized = false;

	// The collection of features that have been registered by unit tests
	std::vector<const base::Feature*>& GetTestFeatures() {
	static base::NoDestructor<std::vector<const base::Feature*>>
	features_for_test;
	return *features_for_test;
	}

	void SetExperimentIds(const base::ListValue& list) {
	DCHECK(!g_experiment_ids_initialized);
	std::unordered_set<int32_t> ids;
	for (size_t i = 0; i < list.GetSize(); ++i) {
	int32_t id;
	if (list.GetInteger(i, &id)) {
	ids.insert(id);
	} else {
	LOG(ERROR) << "Non-integer value found in experiment id list!";
	}
	}
	GetExperimentIds().swap(ids);
	g_experiment_ids_initialized = true;
	}

	} // namespace

	// PLEASE READ!
	// Cast Platform Features are listed below. These features may be
	// toggled via configs fetched from DCS for devices in the field, or via
	// command-line flags set by the developer. For the end-to-end details of the
	// system design, please see go/dcs-experiments.
	//
	// Below are useful steps on how to use these features in your code.
	//
	// 1) Declaring and defining the feature.
	// All Cast Platform Features should be declared in a common file with other
	// Cast Platform Features (ex. chromecast/base/cast_features.h). When
	// defining your feature, you will need to assign a default value. This is
	// the value that the feature will hold until overriden by the server or the
	// command line. Here's an exmaple:
	//
	// const base::Feature kSuperSecretSauce{
	// "enable_super_secret_sauce", base::FEATURE_DISABLED_BY_DEFAULT};
	//
	// IMPORTANT NOTE:
	// The first parameter that you pass in the definition is the feature's name.
	// This MUST match the DCS experiment key for this feature.
	//
	// While Features elsewhere in Chromium alternatively use dashed-case or
	// PascalCase for their names, Chromecast features should use snake_case
	// (lowercase letters separated by underscores). This will ensure that DCS
	// configs, which are passed around as JSON, remain conformant and readable.
	//
	// 2) Using the feature in client code.
	// Using these features in your code is easy. Here's an example:
	//
	// #include “base/feature_list.h”
	// #include “chromecast/base/chromecast_switches.h”
	//
	// std::unique_ptr<Foo> CreateFoo() {
	// if (base::FeatureList::IsEnabled(kSuperSecretSauce))
	// return std::make_unique<SuperSecretFoo>();
	// return std::make_unique<BoringOldFoo>();
	// }
	//
	// base::FeatureList can be called from any thread, in any process, at any
	// time after PreCreateThreads(). It will return whether the feature is
	// enabled.
	//
	// 3) Overriding the default value from the server.
	// For devices in the field, DCS will issue different configs to different
	// groups of devices, allowing us to run experiments on features. These
	// feature settings will manifest on the next boot of cast_shell. In the
	// example, if the latest config for a particular device set the value of
	// kSuperSecretSauce to true, the appropriate code path would be taken.
	// Otherwise, the default value, false, would be used. For more details on
	// setting up experiments, see go/dcs-launch.
	//
	// 4) Overriding the default and server values from the command-line.
	// While the server value trumps the default values, the command line trumps
	// both. Enable features by passing this command line arg to cast_shell:
	//
	// --enable-features=enable_foo,enable_super_secret_sauce
	//
	// Features are separated by commas. Disable features by passing:
	//
	// --disable-features=enable_foo,enable_bar
	//
	// 5) If you add a new feature to the system you must include it in kFeatures
	// This is because the system relies on knowing all of the features so
	// it can properly iterate over all features to detect changes.
	//

	// Begin Chromecast Feature definitions.

	// Allows applications to access media capture devices (webcams/microphones)
	// through getUserMedia API.
	const base::Feature kAllowUserMediaAccess{"allow_user_media_access",
	base::FEATURE_DISABLED_BY_DEFAULT};
	// Enables the use of QUIC in Cast-specific URLRequestContextGetters. See
	// chromecast/browser/url_request_context_factory.cc for usage.
	const base::Feature kEnableQuic{"enable_quic",
	base::FEATURE_DISABLED_BY_DEFAULT};
	// Enables triple-buffer 720p graphics (overriding default graphics buffer
	// settings for a platform).
	const base::Feature kTripleBuffer720{"enable_triple_buffer_720",
	base::FEATURE_DISABLED_BY_DEFAULT};
	// Enables single-buffered graphics (overriding default graphics buffer
	// settings and takes precedence over triple-buffer feature).
	const base::Feature kSingleBuffer{"enable_single_buffer",
	base::FEATURE_DISABLED_BY_DEFAULT};
	// Disable idle sockets closing on memory pressure. See
	// chromecast/browser/url_request_context_factory.cc for usage.
	const base::Feature kDisableIdleSocketsCloseOnMemoryPressure{
	"disable_idle_sockets_close_on_memory_pressure",
	base::FEATURE_DISABLED_BY_DEFAULT};

	// End Chromecast Feature definitions.
	const base::Feature* kFeatures[] = {
	&kAllowUserMediaAccess,
	&kEnableQuic,
	&kTripleBuffer720,
	&kSingleBuffer,
	&kDisableIdleSocketsCloseOnMemoryPressure,
	};

	// An iterator for a base::DictionaryValue. Use an alias for brevity in loops.
	using Iterator = base::DictionaryValue::Iterator;

	std::vector<const base::Feature*> GetInternalFeatures();

	const std::vector<const base::Feature*>& GetFeatures() {
	static const base::NoDestructor<std::vector<const base::Feature*>> features(
	[] {
	auto features = std::vector<const base::Feature*>(
	kFeatures, kFeatures + sizeof(kFeatures) / sizeof(base::Feature*));
	auto internal_features = GetInternalFeatures();
	features.insert(features.end(), internal_features.begin(),
	internal_features.end());
	return features;
	}());
	if (GetTestFeatures().size() > 0)
	return GetTestFeatures();
	return *features;
	}

	void InitializeFeatureList(const base::DictionaryValue& dcs_features,
	const base::ListValue& dcs_experiment_ids,
	const std::string& cmd_line_enable_features,
	const std::string& cmd_line_disable_features,
	const std::string& extra_enable_features,
	const std::string& extra_disable_features) {
	DCHECK(!base::FeatureList::GetInstance());

	// Set the experiments.
	SetExperimentIds(dcs_experiment_ids);

	std::string all_enable_features =
	cmd_line_enable_features + "," + extra_enable_features;
	std::string all_disable_features =
	cmd_line_disable_features + "," + extra_disable_features;

	// Initialize the FeatureList from the command line.
	auto feature_list = std::make_unique<base::FeatureList>();
	feature_list->InitializeFromCommandLine(all_enable_features,
	all_disable_features);

	// Override defaults from the DCS config.
	for (Iterator it(dcs_features); !it.IsAtEnd(); it.Advance()) {
	// Each feature must have its own FieldTrial object. Since experiments are
	// controlled server-side for Chromecast, and this class is designed with a
	// client-side experimentation framework in mind, these parameters are
	// carefully chosen:
	// - The field trial name is unused for our purposes. However, we need to
	// maintain a 1:1 mapping with Features in order to properly store and
	// access parameters associated with each Feature. Therefore, use the
	// Feature's name as the FieldTrial name to ensure uniqueness.
	// - The probability is hard-coded to 100% so that the FeatureList always
	// respects the value from DCS.
	// - The default group is unused; it will be the same for every feature.
	// - Expiration year, month, and day use a special value such that the
	// feature will never expire.
	// - SESSION_RANDOMIZED is used to prevent the need for an
	// entropy_provider. However, this value doesn't matter.
	// - We don't care about the group_id.
	//
	const std::string& feature_name = it.key();
	auto* field_trial = base::FieldTrialList::FactoryGetFieldTrial(
	feature_name, k100PercentProbability, kDefaultDCSFeaturesGroup,
	base::FieldTrialList::kNoExpirationYear, 1 /* month /, 1 / day */,
	base::FieldTrial::SESSION_RANDOMIZED, nullptr);

	bool enabled;
	if (it.value().GetAsBoolean(&enabled)) {
	// A boolean entry simply either enables or disables a feature.
	feature_list->RegisterFieldTrialOverride(
	feature_name,
	enabled ? base::FeatureList::OVERRIDE_ENABLE_FEATURE
	: base::FeatureList::OVERRIDE_DISABLE_FEATURE,
	field_trial);
	continue;
	}

	const base::DictionaryValue* params_dict;
	if (it.value().GetAsDictionary(&params_dict)) {
	// A dictionary entry implies that the feature is enabled.
	feature_list->RegisterFieldTrialOverride(
	feature_name, base::FeatureList::OVERRIDE_ENABLE_FEATURE,
	field_trial);

	// If the feature has not been overriden from the command line, set its
	// parameters accordingly.
	if (!feature_list->IsFeatureOverriddenFromCommandLine(
	feature_name, base::FeatureList::OVERRIDE_DISABLE_FEATURE)) {
	// Build a map of the FieldTrial parameters and associate it to the
	// FieldTrial.
	base::FieldTrialParamAssociator::FieldTrialParams params;
	for (Iterator p(*params_dict); !p.IsAtEnd(); p.Advance()) {
	std::string val;
	if (p.value().GetAsString(&val)) {
	params[p.key()] = val;
	} else {
	LOG(ERROR) << "Entry in params dict for \"" << feature_name << "\""
	<< " feature is not a string. Skipping.";
	}
	}

	// Register the params, so that they can be queried by client code.
	bool success = base::AssociateFieldTrialParams(
	feature_name, kDefaultDCSFeaturesGroup, params);
	DCHECK(success);
	}
	continue;
	}

	// Other base::Value types are not supported.
	LOG(ERROR) << "A DCS feature mapped to an unsupported value. key: "
	<< feature_name << " type: " << it.value().type();
	}

	base::FeatureList::SetInstance(std::move(feature_list));
	}

	bool IsFeatureEnabled(const base::Feature& feature) {
	DCHECK(base::ContainsValue(GetFeatures(), &feature)) << feature.name;
	return base::FeatureList::IsEnabled(feature);
	}

	base::DictionaryValue GetOverriddenFeaturesForStorage(
	const base::Value& features) {
	base::DictionaryValue persistent_dict;

	// \|features\| maps feature names to either a boolean or a dict of params.
	for (const auto& feature : features.DictItems()) {
	if (feature.second.is_bool()) {
	persistent_dict.SetBoolean(feature.first, feature.second.GetBool());
	continue;
	}

	const base::DictionaryValue* params_dict;
	if (feature.second.GetAsDictionary(&params_dict)) {
	auto params = std::make_unique<base::DictionaryValue>();

	bool bval;
	int ival;
	double dval;
	std::string sval;
	for (Iterator p(*params_dict); !p.IsAtEnd(); p.Advance()) {
	const auto& param_key = p.key();
	const auto& param_val = p.value();
	if (param_val.GetAsBoolean(&bval)) {
	params->SetString(param_key, bval ? "true" : "false");
	} else if (param_val.GetAsInteger(&ival)) {
	params->SetString(param_key, base::IntToString(ival));
	} else if (param_val.GetAsDouble(&dval)) {
	params->SetString(param_key, base::NumberToString(dval));
	} else if (param_val.GetAsString(&sval)) {
	params->SetString(param_key, sval);
	} else {
	LOG(ERROR) << "Entry in params dict for \"" << feature.first << "\""
	<< " is not of a supported type (key: " << param_key
	<< ", type: " << param_val.type();
	}
	}
	persistent_dict.Set(feature.first, std::move(params));
	continue;
	}

	// Other base::Value types are not supported.
	LOG(ERROR) << "A DCS feature mapped to an unsupported value. key: "
	<< feature.first << " type: " << feature.second.type();
	}

	return persistent_dict;
	}

	const std::unordered_set<int32_t>& GetDCSExperimentIds() {
	DCHECK(g_experiment_ids_initialized);
	return GetExperimentIds();
	}

	void ResetCastFeaturesForTesting() {
	g_experiment_ids_initialized = false;
	base::FeatureList::ClearInstanceForTesting();
	GetTestFeatures().clear();
	}

	void SetFeaturesForTest(std::vector<const base::Feature*> features) {
	GetTestFeatures() = std::move(features);
	}

	} // namespace chromecast