Store a stacktrace of PrefService destruction in PrefChangeRegistrar

base/prefs/pref_observer.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.
 
 #ifndef BASE_PREFS_PREF_OBSERVER_H_
 #define BASE_PREFS_PREF_OBSERVER_H_
 
 #include <string>
 
 class PrefService;
 
 // Used internally to the Prefs subsystem to pass preference change
 // notifications between PrefService, PrefNotifierImpl and
 // PrefChangeRegistrar.
 class PrefObserver {
  public:
   virtual void OnPreferenceChanged(PrefService* service,
                                    const std::string& pref_name) = 0;
+
+  // TODO(battre): Remove function (debugging tool for crbug.com/373435).
+  virtual void SetPrefServiceDestructionTrace(
+      const std::string& stacktrace) = 0;
 };
 
 #endif  // BASE_PREFS_PREF_OBSERVER_H_