disable field trials if the build is 30 days or older

base/metrics/field_trial.h

 // Copyright (c) 2011 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 94 matching lines @@
   // Return the randomly selected group number that was assigned.
   // Return kNotParticipating if the instance is not participating in the
   // experiment.
   int group() const { return group_; }
 
   // If the field trial is not in an experiment, this returns the empty string.
   // if the group's name is empty, a name of "_" concatenated with the group
   // number is used as the group name.
   std::string group_name() const { return group_name_; }
 
+  // Return true if there is a default group with kAllRemainingProbability.
+  // all_remaining_probability_set_ is set to true when AppendGroup is called
+  // with kAllRemainingProbability as group probability. When MakeName is called
+  // we assert that all_remaining_probability_set_ is set to true.
+  bool all_remaining_probability_set() const {
+    return all_remaining_probability_set_;
+  }
+
+  // Set the usage_timeout from build time of the module to disable Field Trial.
+  void SetUsageTimeout(const base::TimeDelta& usage_timeout);
+  base::TimeDelta usage_timeout() const { return usage_timeout_; }
+
   // 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,
                               const std::string& trial_name);
 
   // Enable benchmarking sets field trials to a common setting.
   static void EnableBenchmarking();
 
  private:
   friend class RefCounted<FieldTrial>;
 
   virtual ~FieldTrial();
 
+  // Determine if the field trial is to be disabled or not based on
+  // usage_timeout_, build time of the module and Now(). This method sets
+  // disable_field_trial_ to true, if the difference between build time of the
+  // module and Now() is greater than usage_timeout_. If disable_field_trial_ is
+  // true then the field trial reverts to the 'default' bucket.
+  static bool ShouldFieldTrialBeDisabled(
+      const base::TimeDelta& usage_timeout);
+
+  // Get build time.
+  static Time GetBuildTime();
+
   // The name of the field trial, as can be found via the FieldTrialList.
   // This is empty of the trial is not in the experiment.
   const std::string name_;
 
   // The maximum sum of all probabilities supplied, which corresponds to 100%.
   // This is the scaling factor used to adjust supplied probabilities.
   Probability divisor_;
 
   // The randomly selected probability that is used to select a group (or have
   // the instance not participate).  It is the product of divisor_ and a random
   // number between [0, 1).
   Probability random_;
 
   // Sum of the probabilities of all appended groups.
   Probability accumulated_group_probability_;
 
   int next_group_number_;
 
   // The pseudo-randomly assigned group number.
   // This is kNotParticipating if no group has been assigned.
   int group_;
 
   // A textual name for the randomly selected group, including the Trial name.
   // If this Trial is not a member of an group, this string is empty.
   std::string group_name_;
 
+  // Set to true if there is a default group with kAllRemainingProbability.
+  bool all_remaining_probability_set_;
+
+  // The default value (all remaining probabilities) can be selected after the
+  // usage_timeout, which is based on the build time of the module.
+  base::TimeDelta usage_timeout_;
+
+  // When disable_field_trial_ is true, field trial reverts to the 'default'
+  // bucket.
+  bool disable_field_trial_;
+
   // When benchmarking is enabled, field trials all revert to the 'default'
   // bucket.
   static bool enable_benchmarking_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrial);
 };
 
 //------------------------------------------------------------------------------
 // Class with a list of all active field trials.  A trial is active if it has
 // been registered, which includes evaluating its state based on its probaility.
@@ skipping 75 matching lines @@
   Lock lock_;
   RegistrationList registered_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialList);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_H_