Fix crash when variation parameters are set in chrome://flags.

components/variations/variations_seed_processor.cc

Index: components/variations/variations_seed_processor.cc
diff --git a/components/variations/variations_seed_processor.cc b/components/variations/variations_seed_processor.cc
index fb4d7e56700188ce290b8ade8c9fcd3c4e8b93c2..dece0a083bd4fddc6add6c57294a471c23b67eae 100644
--- a/components/variations/variations_seed_processor.cc
+++ b/components/variations/variations_seed_processor.cc
@@ -275,6 +275,14 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
           randomization_seed, NULL,
           ShouldStudyUseLowEntropy(study) ? low_entropy_provider : NULL));
 
+  // If the trial previously existed (created from command-line flags or from
+  // about:flags), the factory returns the existing trial keeping its selected
+  // group intact. If this selected group does not exist in this
+  // |processed_study|, we have nothing to do here any more.
+  const std::string& group_name = trial->group_name();

[Alexei Svitkine (slow), 2016/06/30 21:50:59]

Nit: Just inline this into the call below.

[jkrcal, 2016/07/01 10:40:54]

Done.

+  int experiment_index = processed_study.GetExperimentIndexByName(group_name);
+  if (experiment_index == -1) return;

[Alexei Svitkine (slow), 2016/06/30 21:50:59]

Nit: Put return on next line.

[jkrcal, 2016/07/01 10:40:54]

Done.

+
   bool has_overrides = false;
   bool enables_or_disables_features = false;
   for (int i = 0; i < study.experiment_size(); ++i) {
@@ -309,20 +317,11 @@ void VariationsSeedProcessor::CreateTrialFromStudy(
     RegisterFeatureOverrides(processed_study, trial.get(), feature_list);
 
   if (study.activation_type() == Study_ActivationType_ACTIVATION_AUTO) {
-    const std::string& group_name = trial->group_name();
-
     // Don't try to apply overrides if none of the experiments in this study had
     // any.
     if (!has_overrides)
       return;
 
-    // UI Strings can only be overridden from ACTIVATION_AUTO experiments.
-    int experiment_index = processed_study.GetExperimentIndexByName(group_name);
-
-    // The field trial was defined from |study|, so the active experiment's name
-    // must be in the |study|.
-    DCHECK_NE(-1, experiment_index);
-
     ApplyUIStringOverrides(study.experiment(experiment_index),
                            override_callback);
   }