Fix wrong comments about two search engine related variables

components/search_engines/default_search_manager.h

 // Copyright 2014 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 COMPONENTS_SEARCH_ENGINES_DEFAULT_SEARCH_MANAGER_H_
 #define COMPONENTS_SEARCH_ENGINES_DEFAULT_SEARCH_MANAGER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 128 matching lines @@
 
   PrefService* pref_service_;
   const ObserverCallback change_observer_;
   PrefChangeRegistrar pref_change_registrar_;
 
   // Default search engine provided by pre-populated data or by the
   // |kSearchProviderOverrides| pref. This will be used when no other default
   // search engine has been selected.
   scoped_ptr<TemplateURLData> fallback_default_search_;
 
-  // Default search engine provided by prefs (either user prefs or policy
-  // prefs). This will be null if no value was set in the pref store.
-  scoped_ptr<TemplateURLData> extension_default_search_;
-
   // Default search engine provided by extension (usings Settings Override API).
   // This will be null if there are no extensions installed which provide
   // default search engines.
+  scoped_ptr<TemplateURLData> extension_default_search_;
+
+  // Default search engine provided by prefs (either user prefs or policy
+  // prefs). This will be null if no value was set in the pref store.
   scoped_ptr<TemplateURLData> prefs_default_search_;
 
   // True if the default search is currently enforced by policy.
   bool default_search_controlled_by_policy_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultSearchManager);
 };
 
 #endif  // COMPONENTS_SEARCH_ENGINES_DEFAULT_SEARCH_MANAGER_H_