Add variations params api to get params from features.

base/feature_list_unittest.cc

 // Copyright 2015 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 "base/feature_list.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <utility>
@@ skipping 375 matching lines @@
   RegisterFeatureListInstance(std::move(feature_list));
 
   std::string enable_features;
   std::string disable_features;
   FeatureList::GetInstance()->GetFeatureOverrides(&enable_features,
                                                   &disable_features);
   EXPECT_EQ("*OffByDefault<Trial,A,X", SortFeatureListString(enable_features));
   EXPECT_EQ("D", SortFeatureListString(disable_features));
 }
 
+TEST_F(FeatureListTest, GetFieldTrial) {
+  ClearFeatureListInstance();
+  FieldTrialList field_trial_list(nullptr);
+  FieldTrial* trial = FieldTrialList::CreateFieldTrial("Trial", "Group");
+  std::unique_ptr<FeatureList> feature_list(new FeatureList);
+  feature_list->RegisterFieldTrialOverride(
+      kFeatureOnByDefaultName, FeatureList::OVERRIDE_USE_DEFAULT, trial);
+  RegisterFeatureListInstance(std::move(feature_list));
+
+  EXPECT_EQ(trial, FeatureList::GetFieldTrial(kFeatureOnByDefault));
+  EXPECT_EQ(nullptr, FeatureList::GetFieldTrial(kFeatureOffByDefault));
+}
+
 TEST_F(FeatureListTest, InitializeFromCommandLine_WithFieldTrials) {
   ClearFeatureListInstance();
   FieldTrialList field_trial_list(nullptr);
   FieldTrialList::CreateFieldTrial("Trial", "Group");
   std::unique_ptr<FeatureList> feature_list(new FeatureList);
   feature_list->InitializeFromCommandLine("A,OffByDefault<Trial,X", "D");
   RegisterFeatureListInstance(std::move(feature_list));
 
   EXPECT_FALSE(FieldTrialList::IsTrialActive("Trial"));
   EXPECT_TRUE(FeatureList::IsEnabled(kFeatureOffByDefault));
@@ skipping 32 matching lines @@
   EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOnByDefault));
   EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOffByDefault));
 
   // Do not initialize from commandline if we have already.
   FeatureList::InitializeInstance(kFeatureOffByDefaultName, "");
   EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOnByDefault));
   EXPECT_FALSE(FeatureList::IsEnabled(kFeatureOffByDefault));
 }
 
 }  // namespace base