Add and implement API to associate Google experiment IDs with FieldTrials.

base/metrics/field_trial.h

 // 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.
 
 // FieldTrial is a class for handling details of statistical experiments
 // performed by actual users in the field (i.e., in a shipped or beta product).
 // All code is called exclusively on the UI thread currently.
 //
 // The simplest example is an experiment to see whether one of two options
 // produces "better" results across our user population.  In that scenario, UMA
@@ skipping 128 matching lines @@
   // officially chosen, otherwise name_group_id is left untouched and false
   // is returned. When true is returned, the name and group ids were
   // successfully set in name_group_id.
   bool GetNameGroupId(NameGroupId* name_group_id);
 
   // Helper function for the most common use: as an argument to specify the
   // name of a HISTOGRAM.  Use the original histogram name as the name_prefix.
   static std::string MakeName(const std::string& name_prefix,
                               const std::string& trial_name);
 
+  // Helper function to create a NameGroupId from |trial_name| and |group_name|.
+  static NameGroupId MakeNameGroupId(const std::string& trial_name,
+                                     const std::string& group_name);
+
   // Enable benchmarking sets field trials to a common setting.
   static void EnableBenchmarking();
 
  private:
   // Allow tests to access our innards for testing purposes.
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, Registration);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, AbsoluteProbabilities);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, RemainingProbability);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, FiftyFiftyProbability);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, MiddleProbabilities);
@@ skipping 276 matching lines @@
 
   // List of observers to be notified when a group is selected for a FieldTrial.
   ObserverList<Observer> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialList);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_H_