Revert of Reland "[Chromecast] Use base::FeatureList to control features."

chromecast/base/cast_features.cc

Index: chromecast/base/cast_features.cc
diff --git a/chromecast/base/cast_features.cc b/chromecast/base/cast_features.cc
deleted file mode 100644
index 636f145e6df9f2326a16e6ea901cf8fe20f35c66..0000000000000000000000000000000000000000
--- a/chromecast/base/cast_features.cc
+++ /dev/null
@@ -1,197 +0,0 @@
-// 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 "base/command_line.h"
-#include "base/feature_list.h"
-#include "base/lazy_instance.h"
-#include "base/metrics/field_trial.h"
-#include "base/metrics/field_trial_param_associator.h"
-#include "base/metrics/field_trial_params.h"
-#include "base/strings/string_number_conversions.h"
-#include "base/values.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";
-
-base::LazyInstance<std::unordered_set<int32_t>>::Leaky g_experiment_ids =
-    LAZY_INSTANCE_INITIALIZER;
-bool g_experiment_ids_initialized = false;
-
-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!";
-    }
-  }
-  g_experiment_ids.Get().swap(ids);
-  g_experiment_ids_initialized = true;
-}
-}  // namespace
-
-// An iterator for a base::DictionaryValue. Use an alias for brevity in loops.
-using Iterator = base::DictionaryValue::Iterator;
-
-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) {
-  DCHECK(!base::FeatureList::GetInstance());
-
-  // Set the experiments.
-  SetExperimentIds(dcs_experiment_ids);
-
-  // Initialize the FeatureList from the command line.
-  auto feature_list = base::MakeUnique<base::FeatureList>();
-  feature_list->InitializeFromCommandLine(cmd_line_enable_features,
-                                          cmd_line_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));
-}
-
-base::DictionaryValue GetOverriddenFeaturesForStorage(
-    const base::DictionaryValue& features) {
-  base::DictionaryValue persistent_dict;
-
-  // |features| maps feature names to either a boolean or a dict of params.
-  for (Iterator it(features); !it.IsAtEnd(); it.Advance()) {
-    bool enabled;
-    if (it.value().GetAsBoolean(&enabled)) {
-      persistent_dict.SetBoolean(it.key(), enabled);
-      continue;
-    }
-
-    const base::DictionaryValue* params_dict;
-    if (it.value().GetAsDictionary(&params_dict)) {
-      auto params = base::MakeUnique<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::DoubleToString(dval));
-        } else if (param_val.GetAsString(&sval)) {
-          params->SetString(param_key, sval);
-        } else {
-          LOG(ERROR) << "Entry in params dict for \"" << it.key() << "\""
-                     << " is not of a supported type (key: " << p.key()
-                     << ", type: " << param_val.type();
-        }
-      }
-      persistent_dict.Set(it.key(), std::move(params));
-      continue;
-    }
-
-    // Other base::Value types are not supported.
-    LOG(ERROR) << "A DCS feature mapped to an unsupported value. key: "
-               << it.key() << " type: " << it.value().type();
-  }
-
-  return persistent_dict;
-}
-
-const std::unordered_set<int32_t>& GetDCSExperimentIds() {
-  DCHECK(g_experiment_ids_initialized);
-  return g_experiment_ids.Get();
-}
-
-void ResetCastFeaturesForTesting() {
-  g_experiment_ids_initialized = false;
-  base::FeatureList::ClearInstanceForTesting();
-}
-
-}  // namespace chromecast