Store field trial parameters in shared memory

base/metrics/field_trial_param_associator.h

 // Copyright 2016 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.
 
 #ifndef BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_
 #define BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_
 
 #include <map>
 #include <string>
 #include <utility>
@@ skipping 15 matching lines @@
   typedef std::map<std::string, std::string> FieldTrialParams;
 
   // Retrieve the singleton.
   static FieldTrialParamAssociator* GetInstance();
 
   // Sets parameters for the given field trial name and group.
   bool AssociateFieldTrialParams(const std::string& trial_name,
                                  const std::string& group_name,
                                  const FieldTrialParams& params);
 
-  // Gets the parameters for a field trial and its chosen group.
+  // Gets the parameters for a field trial.
   bool GetFieldTrialParams(const std::string& trial_name,
                            FieldTrialParams* params);
 
+  // Gets the parameters for a field trial. Caller must lock.
+  bool GetFieldTrialParamsWhileLocked(const std::string& trial_name,

[Alexei Svitkine (slow), 2016/11/01 14:57:16]

This is not correct.

The lock in question is the one in this object. Since it's private, the caller
can't lock it.

Why not just use GetFieldTrialParams()?

[lawrencewu, 2016/11/01 18:29:05]

Fixed by overloading GetFieldTrialParams() and calling that.

+                                      const std::string& group_name,
+                                      FieldTrialParams* params);
+
   // Clears the internal field_trial_params_ mapping.
   void ClearAllParamsForTesting();
 
  private:
   friend struct DefaultSingletonTraits<FieldTrialParamAssociator>;
 
   // (field_trial_name, field_trial_group)
   typedef std::pair<std::string, std::string> FieldTrialKey;
 
   Lock lock_;
   std::map<FieldTrialKey, FieldTrialParams> field_trial_params_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialParamAssociator);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_PARAM_ASSOCIATOR_H_