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base/metrics/field_trial.h

Index: base/metrics/field_trial.h
diff --git a/base/metrics/field_trial.h b/base/metrics/field_trial.h
index e2e543947a10a97595b828c63a432c7710aaab79..c5e87ea0ec874e52994072954a1a0266b8803596 100644
--- a/base/metrics/field_trial.h
+++ b/base/metrics/field_trial.h
@@ -106,7 +106,16 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
     std::string group_name;
   };
 
+  // A triplet representing a Field Trial, its selected group and whether it's
+  // active.
+  struct FieldTrialState {
+    std::string trial_name;
+    std::string group_name;
+    bool activated;
+  };
+
   typedef std::vector<ActiveGroup> ActiveGroups;
+  typedef std::vector<FieldTrialState> AllGroups;
 
   // A return value to indicate that a given instance has not yet had a group
   // assignment (and hence is not yet participating in the trial).
@@ -180,6 +189,7 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, OneWinner);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, DisableProbability);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, ActiveGroups);
+  FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, AllGroups);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, ActiveGroupsNotFinalized);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, Save);
   FRIEND_TEST_ALL_PREFIXES(FieldTrialTest, DuplicateRestore);
@@ -230,6 +240,13 @@ class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> {
   // untouched.
   bool GetActiveGroup(ActiveGroup* active_group) const;
 
+  // Returns the trial name and selected group name for this field trial via
+  // the output parameter |field_trial_state|, but only if the trial has not
+  // been disabled. In that case, true is returned and |field_trial_state| is
+  // filled in; otherwise, the result is false and |field_trial_state| is left
+  // untouched.
+  bool GetFieldTrialState(FieldTrialState* field_trial_state) const;

[Alexei Svitkine (slow), 2014/11/05 22:50:53]

Nit: Actually, just name this GetState().

[Georges Khalil, 2014/11/06 18:36:28]

Done.

+
   // Returns the group_name. A winner need not have been chosen.
   std::string group_name_internal() const { return group_name_; }
 
@@ -404,6 +421,16 @@ class BASE_EXPORT FieldTrialList {
   // by |CreateTrialsFromString()|.
   static void StatesToString(std::string* output);
 
+  // Creates a persistent representation of all FieldTrial instances for
+  // resurrection in another process. This allows randomization to be done in
+  // one process, and secondary processes can be synchronized on the result.
+  // The resulting string contains the name and group name pairs of all
+  // registered FieldTrials which have not been disabled, with "/" used
+  // to separate all names and to terminate the string. All activated trials
+  // have their name prefixed with "*". This string is parsed by
+  // |CreateTrialsFromString()|.
+  static void AllStatesToString(std::string* output);
+
   // Fills in the supplied vector |active_groups| (which must be empty when
   // called) with a snapshot of all registered FieldTrials for which the group
   // has been chosen and externally observed (via |group()|) and which have
@@ -450,6 +477,11 @@ class BASE_EXPORT FieldTrialList {
   static size_t GetFieldTrialCount();
 
  private:
+  // Fills in the supplied vector |all_groups| (which must be empty when called)
+  // with a snapshot of all registered FieldTrials which have not been disabled.
+  static void GetAllFieldTrialGroups(
+      FieldTrial::AllGroups* all_groups);
+
   // A map from FieldTrial names to the actual instances.
   typedef std::map<std::string, FieldTrial*> RegistrationMap;