Extend VariationParamsManager to support feature associations.

components/variations/variations_params_manager.cc

Index: components/variations/variations_params_manager.cc
diff --git a/components/variations/variations_params_manager.cc b/components/variations/variations_params_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..18fb36d507905c03f2e65846e4421e6d9417f439
--- /dev/null
+++ b/components/variations/variations_params_manager.cc
@@ -0,0 +1,91 @@
+// Copyright 2016 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/variations/variations_params_manager.h"
+
+#include <utility>
+
+#include "base/feature_list.h"
+#include "base/metrics/field_trial.h"
+#include "base/test/scoped_feature_list.h"
+#include "components/variations/variations_associated_data.h"
+
+namespace variations {
+namespace testing {
+
+namespace {
+
+const char kGroupTesting[] = "Testing";

[Alexei Svitkine (slow), 2016/11/24 19:29:40]

Nit: Add a comment about how this is used.

[jkrcal, 2016/11/25 13:23:37]

Done.

+
+base::FieldTrial* CreateFieldTrialWithParams(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& param_values) {
+  variations::AssociateVariationParams(trial_name, kGroupTesting, param_values);

[Alexei Svitkine (slow), 2016/11/24 19:29:40]

Nit: No need for variations:: here

[jkrcal, 2016/11/25 13:23:37]

Done.

+  return base::FieldTrialList::CreateFieldTrial(trial_name, kGroupTesting);
+}
+
+}  // namespace
+
+VariationParamsManager::VariationParamsManager()
+    : field_trial_list_(new base::FieldTrialList(nullptr)),
+      scoped_feature_list_(new base::test::ScopedFeatureList()) {}
+
+VariationParamsManager::VariationParamsManager(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& param_values)
+    : VariationParamsManager() {
+  SetVariationParams(trial_name, param_values);
+}
+
+VariationParamsManager::VariationParamsManager(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& param_values,
+    const std::set<std::string>& associated_features)
+    : VariationParamsManager() {
+  SetVariationParamsWithFeatureAssociations(trial_name, param_values,
+                                            associated_features);
+}
+
+VariationParamsManager::~VariationParamsManager() {
+  ClearAllVariationIDs();
+  ClearAllVariationParams();
+}
+
+void VariationParamsManager::SetVariationParams(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& param_values) {
+  CreateFieldTrialWithParams(trial_name, param_values);
+}
+
+void VariationParamsManager::SetVariationParamsWithFeatureAssociations(
+    const std::string& trial_name,
+    const std::map<std::string, std::string>& param_values,
+    const std::set<std::string>& associated_features) {
+  base::FieldTrial* field_trial =
+      CreateFieldTrialWithParams(trial_name, param_values);
+
+  std::unique_ptr<base::FeatureList> feature_list(new base::FeatureList);
+  for (const std::string& feature_name : associated_features) {
+    feature_list->RegisterFieldTrialOverride(
+              feature_name,
+              base::FeatureList::OverrideState::OVERRIDE_ENABLE_FEATURE,
+              field_trial);
+  }
+
+  scoped_feature_list_->InitWithFeatureList(std::move(feature_list));
+}
+
+void VariationParamsManager::ClearAllVariationIDs() {
+  variations::testing::ClearAllVariationIDs();

[Alexei Svitkine (slow), 2016/11/24 19:29:40]

Nit: Remove namespaces

[jkrcal, 2016/11/25 13:23:37]

I guess I cannot remove it here and below as it would resolve to the function in
this class (cycling into a stack overflow).

+}
+
+void VariationParamsManager::ClearAllVariationParams() {
+  variations::testing::ClearAllVariationParams();

[Alexei Svitkine (slow), 2016/11/24 19:29:40]

Nit: Ditto.

[jkrcal, 2016/11/25 13:23:37]

Ditto.

+  // When the scoped feature list is destroyed, it puts back the original
+  // feature list that was there when InitWithFeatureList() was called.
+  scoped_feature_list_.reset(new base::test::ScopedFeatureList());
+}
+
+}  // namespace testing
+}  // namespace variations