Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/app_indicator_icon_menu.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/app_indicator_icon_menu.h"
+#include "chrome/browser/ui/libgtkui/app_indicator_icon_menu.h"
 
 #include <gtk/gtk.h>
 
 #include "base/bind.h"
 #include "base/debug/leak_annotations.h"
-#include "chrome/browser/ui/libgtk2ui/menu_util.h"
+#include "chrome/browser/ui/libgtkui/menu_util.h"
 #include "ui/base/models/menu_model.h"
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 AppIndicatorIconMenu::AppIndicatorIconMenu(ui::MenuModel* model)
     : menu_model_(model),
       click_action_replacement_menu_item_added_(false),
       gtk_menu_(NULL),
       block_activation_(false) {
   {
     ANNOTATE_SCOPED_MEMORY_LEAK; // http://crbug.com/378770
     gtk_menu_ = gtk_menu_new();
   }
@@ skipping 88 matching lines @@
 
   int id;
   if (!GetMenuItemID(menu_item, &id))
     return;
 
   // The menu item can still be activated by hotkeys even if it is disabled.
   if (menu_model_->IsEnabledAt(id))
     ExecuteCommand(model, id);
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui