Eliminate BrowserProcess dependency from sign-in production code.

base/prefs/pref_change_registrar.cc

 // Copyright (c) 2010 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.
 
 #include "base/prefs/pref_change_registrar.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 
@@ skipping 71 matching lines @@
 }
 
 void PrefChangeRegistrar::InvokeUnnamedCallback(const base::Closure& callback,
                                                 const std::string& pref_name) {
   callback.Run();
 }
 
 PrefService* PrefChangeRegistrar::prefs() {
   return service_;
 }
+
+const PrefService* PrefChangeRegistrar::prefs() const {
+  return service_;
+}