[Field trials] Allow default group names to be omitted.

components/variations/variations_seed_simulator.cc

 // Copyright 2014 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_seed_simulator.h"
 
 #include <stddef.h>
 
 #include <map>
 
@@ skipping 25 matching lines @@
     const ProcessedStudy& processed_study) {
   const Study& study = *processed_study.study();
   DCHECK_EQ(Study_Consistency_PERMANENT, study.consistency());
 
   const double entropy_value =
       entropy_provider.GetEntropyForTrial(study.name(),
                                           study.randomization_seed());
   scoped_refptr<base::FieldTrial> trial(
       base::FieldTrial::CreateSimulatedFieldTrial(
           study.name(), processed_study.total_probability(),
-          study.default_experiment_name(), entropy_value));
+          processed_study.GetDefaultExperimentName(), entropy_value));
 
   for (int i = 0; i < study.experiment_size(); ++i) {
     const Study_Experiment& experiment = study.experiment(i);
     // TODO(asvitkine): This needs to properly handle the case where a group was
     // forced via forcing_flag in the current state, so that it is not treated
     // as changed.
     if (!experiment.has_forcing_flag() &&
         experiment.name() != study.default_experiment_name()) {
       trial->AppendGroup(experiment.name(), experiment.probability_weight());
     }
@@ skipping 199 matching lines @@
     return ConvertExperimentTypeToChangeType(experiment->type());
   }
 
   // Current group exists in the study - check whether its params changed.
   if (!VariationParamsAreEqual(study, *experiment))
     return ConvertExperimentTypeToChangeType(experiment->type());
   return NO_CHANGE;
 }
 
 }  // namespace variations