Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_event_loop.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_LIBGTK2UI_GTK2_EVENT_LOOP_H_
-#define CHROME_BROWSER_UI_LIBGTK2UI_GTK2_EVENT_LOOP_H_
+#ifndef CHROME_BROWSER_UI_LIBGTKUI_GTK2_EVENT_LOOP_H_
+#define CHROME_BROWSER_UI_LIBGTKUI_GTK2_EVENT_LOOP_H_
 
 #include "base/macros.h"
 #include "ui/base/glib/glib_integers.h"
 
 typedef union _GdkEvent GdkEvent;
 typedef struct _GdkEventKey GdkEventKey;
 
 namespace base {
 template<typename Type> struct DefaultSingletonTraits;
 }
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 class Gtk2EventLoop {
  public:
   static Gtk2EventLoop* GetInstance();
 
  private:
   friend struct base::DefaultSingletonTraits<Gtk2EventLoop>;
 
   Gtk2EventLoop();
   ~Gtk2EventLoop();
 
   static void DispatchGdkEvent(GdkEvent* gdk_event, gpointer);
   static void ProcessGdkEventKey(const GdkEventKey& gdk_event_key);
 
   DISALLOW_COPY_AND_ASSIGN(Gtk2EventLoop);
 };
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui
 
-#endif  // CHROME_BROWSER_UI_LIBGTK2UI_GTK2_EVENT_LOOP_H_
+#endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK2_EVENT_LOOP_H_