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)
@@ -112,6 +112,17 @@
   // number is used as the group name.
   std::string group_name() const { return group_name_; }
 
+  // Set the duration after which we will disable Field Trials. We will subtract
+  // build time from application start time and if the difference is greater
+  // than the duration that is specified via the following function, then we
+  // disable field trails and the field trials revert to the 'default' bucket.
+  void SetDurationAfterWhichDisableFieldTrials(base::TimeDelta duration) {

[jar (doing other things), 2011/01/09 07:00:04]

nit: for classes as arguments, pass in:
const CLASSNAME&

[jar (doing other things), 2011/01/09 07:00:04]

nit: Since this is an instance of FieldTrial, we only control this one single
field trial with this setting, so the name of the method should not end in an
"s" (we don't impact TrialS).

In fact, since this is a FieldTrial method, we probably don't need the
FieldTrial posfix.

That would get the name down to something like:

SetDurationAfterWhichDisabled

Which might even be written:

SetDisableDuration

The slot describing the corresponding member (disable_duration_??) would have a
comment that only the default value (all remaining probabilities) can be
selected after the duration, which is based on the build time of the module.

WDYT?

[rtenneti, 2011/01/09 23:16:42]

Done.

[rtenneti, 2011/01/09 23:16:42]

Done.

+    duration_after_which_disable_field_trials_ = duration;
+  }
+  base::TimeDelta durationAfterWhichDisableFieldTrials() {
+    return duration_after_which_disable_field_trials_;
+  }
+
   // 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 +131,9 @@
   // 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 +157,11 @@
 
   int next_group_number_;
 
+  // duration after which we should disable field_trails.
+  base::TimeDelta duration_after_which_disable_field_trials_;
+
+  bool disable_field_trails_;
+
   // The pseudo-randomly assigned group number.
   // This is kNotParticipating if no group has been assigned.
   int group_;