RefCounted types should not have public destructors, chrome/browser/ part 6

chrome/browser/metrics/field_trial_synchronizer.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.
 
 #ifndef CHROME_BROWSER_METRICS_FIELD_TRIAL_SYNCHRONIZER_H_
 #define CHROME_BROWSER_METRICS_FIELD_TRIAL_SYNCHRONIZER_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 17 matching lines @@
       public base::FieldTrialList::Observer {
  public:
   // Construction also sets up the global singleton instance.  This instance is
   // used to communicate between the UI and other threads, and is destroyed only
   // as the main thread (browser_main) terminates, which means all other threads
   // have completed, and will not need this instance any further. It adds itself
   // as an observer of FieldTrialList so that it gets notified whenever a group
   // is finalized in the browser process.
   FieldTrialSynchronizer();
 
-  virtual ~FieldTrialSynchronizer();
-
   // Notify all renderer processes about the |group_name| that is finalized for
   // the given field trail (|field_trial_name|). This is called on UI thread.
   void NotifyAllRenderers(const std::string& field_trial_name,
                           const std::string& group_name);
 
   // FieldTrialList::Observer methods:
 
   // This method is called by the FieldTrialList singleton when a trial's group
   // is finalized. This method contacts all renderers (by calling
   // NotifyAllRenderers) to create a FieldTrial that carries the randomly
   // selected state from the browser process into all the renderer processes.
   virtual void OnFieldTrialGroupFinalized(
       const std::string& name,
       const std::string& group_name) OVERRIDE;
 
  private:
-  // This singleton instance should be constructed during the single threaded
-  // portion of main(). It initializes globals to provide support for all future
-  // calls. This object is created on the UI thread, and it is destroyed after
-  // all the other threads have gone away.
-  static FieldTrialSynchronizer* field_trial_synchronizer_;
+  friend class base::RefCountedThreadSafe<FieldTrialSynchronizer>;
+  virtual ~FieldTrialSynchronizer();
 
   DISALLOW_COPY_AND_ASSIGN(FieldTrialSynchronizer);
 };
 
 #endif  // CHROME_BROWSER_METRICS_FIELD_TRIAL_SYNCHRONIZER_H_