Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/gtk2_ui.h

 // Copyright (c) 2013 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_UI_H_
-#define CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UI_H_
+#ifndef CHROME_BROWSER_UI_LIBGTKUI_GTK2_UI_H_
+#define CHROME_BROWSER_UI_LIBGTKUI_GTK2_UI_H_
 
 #include <map>
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
-#include "chrome/browser/ui/libgtk2ui/gtk2_signal.h"
-#include "chrome/browser/ui/libgtk2ui/libgtk2ui_export.h"
+#include "chrome/browser/ui/libgtkui/gtk2_signal.h"
+#include "chrome/browser/ui/libgtkui/libgtkui_export.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/views/linux_ui/linux_ui.h"
 #include "ui/views/window/frame_buttons.h"
 
 typedef struct _GtkStyle GtkStyle;
 typedef struct _GtkWidget GtkWidget;
 
 class SkBitmap;
 
-namespace libgtk2ui {
+namespace libgtkui {
 class Gtk2KeyBindingsHandler;
 class GConfListener;
 
 // Interface to GTK2 desktop features.
 //
 class Gtk2UI : public views::LinuxUI {
  public:
   Gtk2UI();
   ~Gtk2UI() override;
 
@@ skipping 161 matching lines @@
   // Used to override the native theme for a window. If no override is provided
   // or the callback returns NULL, Gtk2UI will default to a NativeThemeGtk2
   // instance.
   NativeThemeGetter native_theme_overrider_;
 
   float device_scale_factor_;
 
   DISALLOW_COPY_AND_ASSIGN(Gtk2UI);
 };
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui
 
 // Access point to the GTK2 desktop system. This should be the only symbol that
 // is exported in the library; everything else should be used through the
 // interface, because eventually this .so will be loaded through dlopen at
 // runtime so our main binary can conditionally load GTK2 or GTK3 or EFL or
 // QT or whatever.
-LIBGTK2UI_EXPORT views::LinuxUI* BuildGtk2UI();
+LIBGTKUI_EXPORT views::LinuxUI* BuildGtk2UI();
 
-#endif  // CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UI_H_
+#endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK2_UI_H_