Call CheckTrialGroup only under lock.

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 596 matching lines @@
   {
     AutoLock auto_lock(global_->lock_);
     if (field_trial->group_reported_)
       return;
     field_trial->group_reported_ = true;
   }
 
   if (!field_trial->enable_field_trial_)
     return;
 
-  CheckTrialGroup(field_trial->trial_name(), field_trial->group_name_internal(),
-                  &global_->seen_states_);
+  {
+    AutoLock auto_lock(global_->lock_);
+    CheckTrialGroup(field_trial->trial_name(),
+                    field_trial->group_name_internal(), &global_->seen_states_);
+  }
   global_->observer_list_->Notify(
       FROM_HERE, &FieldTrialList::Observer::OnFieldTrialGroupFinalized,
       field_trial->trial_name(), field_trial->group_name_internal());
 }
 
 // static
 size_t FieldTrialList::GetFieldTrialCount() {
   if (!global_)
     return 0;
   AutoLock auto_lock(global_->lock_);
@@ skipping 25 matching lines @@
     return;
   }
   AutoLock auto_lock(global_->lock_);
   CHECK(!global_->PreLockedFind(trial->trial_name())) << trial->trial_name();
   trial->AddRef();
   trial->SetTrialRegistered();
   global_->registered_[trial->trial_name()] = trial;
 }
 
 }  // namespace base