disable field trials if the build is 30 days or older

base/metrics/field_trial.h

Index: base/metrics/field_trial.h
===================================================================
--- base/metrics/field_trial.h	(revision 70854)
+++ base/metrics/field_trial.h	(working copy)
@@ -94,6 +94,13 @@
   // to the total_probability.
   FieldTrial(const std::string& name, Probability total_probability);
 
+  // Determine if the field trial is to be disabled or not based on
+  // disable_duration_, build time of the module and Now(). This method sets
+  // disable_field_trail_ to true, if the difference between build time of the
+  // module and Now() is greater than disable_duration_. If disable_field_trail_
+  // is true then the field trial reverts to the 'default' bucket.
+  void FieldTrial::DetermineIfFieldTrailIsToBeDisabled();
+
   // Establish the name and probability of the next group in this trial.
   // Sometimes, based on construction randomization, this call may causes the
   // provided group to be *THE* group selected for use in this instance.
@@ -112,6 +119,13 @@
   // number is used as the group name.
   std::string group_name() const { return group_name_; }
 
+  // Set the duration from build time of the module to disable Field Trial.
+  void SetDisableDuration(const base::TimeDelta& duration);
+
+  base::TimeDelta disableDuration() const {
+    return disable_duration_;
+  }
+
   // Helper function for the most common use: as an argument to specifiy the
   // name of a HISTOGRAM.  Use the original histogram name as the name_prefix.
   static std::string MakeName(const std::string& name_prefix,
@@ -120,6 +134,9 @@
   // Enable benchmarking sets field trials to a common setting.
   static void EnableBenchmarking();
 
+  // Get build time.
+  static Time GetBuildTime();
+
  private:
   friend class RefCounted<FieldTrial>;
 
@@ -143,6 +160,14 @@
 
   int next_group_number_;
 
+  // The default value (all remaining probabilities) can be selected after the
+  // duration, which is based on the build time of the module.
+  base::TimeDelta disable_duration_;
+
+  // When disable_field_trail_ is true, field trial reverts to the 'default'
+  // bucket.
+  bool disable_field_trail_;
+
   // The pseudo-randomly assigned group number.
   // This is kNotParticipating if no group has been assigned.
   int group_;