Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_util.cc

 // Copyright (c) 2012 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_util.h"
+#include "chrome/browser/ui/libgtkui/gtk2_util.h"
 
 #include <gdk/gdk.h>
 #include <gdk/gdkx.h>
 #include <gtk/gtk.h>
 #include <stddef.h>
 
 #include <memory>
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 27 matching lines @@
     ANNOTATE_SCOPED_MEMORY_LEAK;
     init_func(&argc, &argv_pointer);
   }
   for (size_t i = 0; i < args.size(); ++i) {
     free(argv[i]);
   }
 }
 
 }  // namespace
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 void GtkInitFromCommandLine(const base::CommandLine& command_line) {
   CommonInitFromCommandLine(command_line, gtk_init);
 }
 
 // TODO(erg): This method was copied out of shell_integration_linux.cc. Because
 // of how this library is structured as a stand alone .so, we can't call code
 // from browser and above.
 std::string GetDesktopName(base::Environment* env) {
 #if defined(GOOGLE_CHROME_BUILD)
@@ skipping 70 matching lines @@
 
 aura::Window* GetAuraTransientParent(GtkWidget* dialog) {
   return reinterpret_cast<aura::Window*>(
       g_object_get_data(G_OBJECT(dialog), kAuraTransientParent));
 }
 
 void ClearAuraTransientParent(GtkWidget* dialog) {
   g_object_set_data(G_OBJECT(dialog), kAuraTransientParent, NULL);
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui