Gtk: Change NULL to nullptr

chrome/browser/ui/libgtkui/gconf_listener.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 CHROME_BROWSER_UI_LIBGTKUI_GCONF_LISTENER_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_GCONF_LISTENER_H_
 
 #include <gconf/gconf-client.h>
 #include <gtk/gtk.h>
 
@@ skipping 28 matching lines @@
   // to GConf and reverts to default mode.
   bool HandleGError(GError* error, const char* key);
 
   // Parses the return data structure from GConf, falling back to the default
   // value on any error.
   void ParseAndStoreButtonValue(GConfValue* gconf_value);
   void ParseAndStoreMiddleClickValue(GConfValue* gconf_value);
 
   GtkUi* delegate_;
 
-  // Pointer to our gconf context. NULL if we aren't on a desktop that uses
+  // Pointer to our gconf context. nullptr if we aren't on a desktop that uses
   // gconf.
   GConfClient* client_;
 
   DISALLOW_COPY_AND_ASSIGN(GConfListener);
 };
 
 }  // namespace libgtkui
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_GCONF_LISTENER_H_