Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_status_icon.cc

 // 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.
 
-#include "chrome/browser/ui/libgtk2ui/gtk2_status_icon.h"
+#include "chrome/browser/ui/libgtkui/gtk2_status_icon.h"
 
 #include <gtk/gtk.h>
 
 #include "base/strings/utf_string_conversions.h"
-#include "chrome/browser/ui/libgtk2ui/app_indicator_icon_menu.h"
-#include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
+#include "chrome/browser/ui/libgtkui/app_indicator_icon_menu.h"
+#include "chrome/browser/ui/libgtkui/skia_utils_gtk2.h"
 #include "ui/base/models/menu_model.h"
 #include "ui/gfx/image/image_skia.h"
 
 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 Gtk2StatusIcon::Gtk2StatusIcon(const gfx::ImageSkia& image,
                                const base::string16& tool_tip) {
   GdkPixbuf* pixbuf = GdkPixbufFromSkBitmap(*image.bitmap());
   gtk_status_icon_ = gtk_status_icon_new_from_pixbuf(pixbuf);
   g_object_unref(pixbuf);
 
   g_signal_connect(gtk_status_icon_, "activate", G_CALLBACK(OnClickThunk),
       this);
   g_signal_connect(gtk_status_icon_, "popup_menu",
@@ skipping 40 matching lines @@
     gtk_menu_popup(menu_->GetGtkMenu(),
                    NULL,
                    NULL,
                    gtk_status_icon_position_menu,
                    gtk_status_icon_,
                    button,
                    activate_time);
   }
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui