Add a death test to check field trial creation before FieldTrialList.

base/metrics/field_trial.cc

 // Copyright (c) 2012 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/metrics/field_trial.h"
 
 #include <algorithm>
 
 #include "base/build_time.h"
 #include "base/logging.h"
@@ skipping 302 matching lines @@
             kNonConflictingGroupNumber != FieldTrial::kNotFinalized,
             conflicting_default_group_number);
         *default_group_number = kNonConflictingGroupNumber;
       }
     }
     return existing_trial;
   }
 
   double entropy_value;
   if (randomization_type == FieldTrial::ONE_TIME_RANDOMIZED) {
-    entropy_value = GetEntropyProviderForOneTimeRandomization()->
-          GetEntropyForTrial(trial_name, randomization_seed);
+    const FieldTrial::EntropyProvider* entropy_provider =
+        GetEntropyProviderForOneTimeRandomization();
+    CHECK(entropy_provider);
+    entropy_value = entropy_provider->GetEntropyForTrial(trial_name,
+                                                         randomization_seed);
   } else {
     DCHECK_EQ(FieldTrial::SESSION_RANDOMIZED, randomization_type);
     DCHECK_EQ(0U, randomization_seed);
     entropy_value = RandDouble();
   }
 
   FieldTrial* field_trial = new FieldTrial(trial_name, total_probability,
                                            default_group_name, entropy_value);
   if (GetBuildTime() > CreateTimeFromParams(year, month, day_of_month))
     field_trial->Disable();
@@ skipping 198 matching lines @@
     return;
   }
   AutoLock auto_lock(global_->lock_);
   DCHECK(!global_->PreLockedFind(trial->trial_name()));
   trial->AddRef();
   trial->SetTrialRegistered();
   global_->registered_[trial->trial_name()] = trial;
 }
 
 }  // namespace base