base: Use std::move() instead of Pass() for real movable types.

base/prefs/pref_service_factory.cc

 // 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.
 
 #include "base/prefs/pref_service_factory.h"
 
 #include "base/bind.h"
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/json_pref_store.h"
 #include "base/prefs/pref_filter.h"
@@ skipping 41 matching lines @@
                                          extension_prefs_.get(),
                                          command_line_prefs_.get(),
                                          user_prefs_.get(),
                                          recommended_prefs_.get(),
                                          pref_registry->defaults().get(),
                                          pref_notifier),
                       user_prefs_.get(),
                       pref_registry,
                       read_error_callback_,
                       async_));
-  return pref_service.Pass();
+  return pref_service;
 }
 
 }  // namespace base