Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_util.h

 // 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.
 
-#ifndef CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UTIL_H_
-#define CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UTIL_H_
+#ifndef CHROME_BROWSER_UI_LIBGTKUI_GTK2_UTIL_H_
+#define CHROME_BROWSER_UI_LIBGTKUI_GTK2_UTIL_H_
 
 #include <gtk/gtk.h>
 #include <string>
 
 #include "ui/native_theme/native_theme.h"
 
 class SkBitmap;
 
 namespace aura {
 class Window;
 }
 
 namespace base {
 class CommandLine;
 class Environment;
 }
 
 namespace ui {
 class Accelerator;
 }
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 void GtkInitFromCommandLine(const base::CommandLine& command_line);
 
 // Returns the name of the ".desktop" file associated with our running process.
 std::string GetDesktopName(base::Environment* env);
 
 guint GetGdkKeyCodeForAccelerator(const ui::Accelerator& accelerator);
 
 GdkModifierType GetGdkModifierForAccelerator(
     const ui::Accelerator& accelerator);
 
 // Translates event flags into plaform independent event flags.
 int EventFlagsFromGdkState(guint state);
 
 // Style a GTK button as a BlueButton
 void TurnButtonBlue(GtkWidget* button);
 
 // Sets |dialog| as transient for |parent|, which will keep it on top and center
 // it above |parent|. Do nothing if |parent| is NULL.
 void SetGtkTransientForAura(GtkWidget* dialog, aura::Window* parent);
 
 // Gets the transient parent aura window for |dialog|.
 aura::Window* GetAuraTransientParent(GtkWidget* dialog);
 
 // Clears the transient parent for |dialog|.
 void ClearAuraTransientParent(GtkWidget* dialog);
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui
 
-#endif  // CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UTIL_H_
+#endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK2_UTIL_H_