Prevent GetDeviceId from invoking its callback multiple times in failure cases.

chrome/browser/prefs/pref_metrics_service.h

 // Copyright 2013 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_PREFS_PREF_METRICS_SERVICE_H_
 #define CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_
 
 #include <map>
 #include <string>
 
@@ skipping 107 matching lines @@
   void InitializePrefObservers();
 
   Profile* profile_;
   PrefService* prefs_;
   PrefService* local_state_;
   std::string profile_name_;
   std::string pref_hash_seed_;
   std::string device_id_;
   const char** tracked_pref_paths_;
   const int tracked_pref_path_count_;
+
+  // TODO(gab): preprocessor define this member out on builds that don't use
+  // DCHECKs (http://crbug.com/322713).
   bool checked_tracked_prefs_;
 
   PrefChangeRegistrar pref_registrar_;
   scoped_ptr<SyncedPrefChangeRegistrar> synced_pref_change_registrar_;
 
   base::WeakPtrFactory<PrefMetricsService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefMetricsService);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_