Make some field trials unforceable via command-line in the official build.

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 271 matching lines @@
 
   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.
 // Only one instance of this class exists.
 class BASE_EXPORT FieldTrialList {
  public:
+  // A callback that returns true if |name| describes a field trial that should
+  // be accepted by the method it was passed to.
+  typedef base::Callback<bool(const std::string& name)>

[Alexei Svitkine (slow), 2014/02/11 22:44:02]

The header for this should probably be included.

[gab, 2014/02/11 22:53:55]

Done.

+      IsAcceptedFieldTrialCallback;
+
   // Specifies whether field trials should be activated (marked as "used"), when
   // created using |CreateTrialsFromString()|.
   enum FieldTrialActivationMode {
     DONT_ACTIVATE_TRIALS,
     ACTIVATE_TRIALS,
   };
 
   // Define a separator character to use when creating a persistent form of an
   // instance.  This is intended for use as a command line argument, passed to a
   // second process to mimic our state (i.e., provide the same group name).
@@ skipping 103 matching lines @@
   static void GetActiveFieldTrialGroups(
       FieldTrial::ActiveGroups* active_groups);
 
   // Use a state string (re: StatesToString()) to augment the current list of
   // field trials to include the supplied trials, and using a 100% probability
   // for each trial, force them to have the same group string. This is commonly
   // used in a non-browser process, to carry randomly selected state in a
   // browser process into this non-browser process, but could also be invoked
   // through a command line argument to the browser process. The created field
   // trials are marked as "used" for the purposes of active trial reporting if
-  // |mode| is ACTIVATE_TRIALS.
-  static bool CreateTrialsFromString(const std::string& prior_trials,
-                                     FieldTrialActivationMode mode);
+  // |mode| is ACTIVATE_TRIALS. If |is_accepted_callback| is not null: field
+  // trials for which |is_accepted_callback| returns false are ignored.
+  static bool CreateTrialsFromString(
+      const std::string& prior_trials,
+      FieldTrialActivationMode mode,
+      const IsAcceptedFieldTrialCallback& is_accepted_callback);
 
   // Create a FieldTrial with the given |name| and using 100% probability for
   // the FieldTrial, force FieldTrial to have the same group string as
   // |group_name|. This is commonly used in a non-browser process, to carry
   // randomly selected state in a browser process into this non-browser process.
   // It returns NULL if there is a FieldTrial that is already registered with
   // the same |name| but has different finalized group string (|group_name|).
   static FieldTrial* CreateFieldTrial(const std::string& name,
                                       const std::string& group_name);
 
@@ skipping 46 matching lines @@
 
   // List of observers to be notified when a group is selected for a FieldTrial.
   scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialList);
 };
 
 }  // namespace base
 
 #endif  // BASE_METRICS_FIELD_TRIAL_H_