Write a NativeThemeGtk2 class for linux_aura.

chrome/browser/ui/libgtk2ui/gtk2_ui.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_ui.h"
 
 #include <set>
 
 #include "base/command_line.h"
 #include "base/i18n/rtl.h"
 #include "base/logging.h"
 #include "base/nix/mime_util_xdg.h"
 #include "base/stl_util.h"
 #include "chrome/browser/themes/theme_properties.h"
 #include "chrome/browser/ui/libgtk2ui/chrome_gtk_frame.h"
 #include "chrome/browser/ui/libgtk2ui/gtk2_util.h"
+#include "chrome/browser/ui/libgtk2ui/native_theme_gtk2.h"
 #include "chrome/browser/ui/libgtk2ui/select_file_dialog_impl.h"
 #include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
 #include "grit/theme_resources.h"
 #include "grit/ui_resources.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "third_party/skia/include/core/SkShader.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/canvas.h"
@@ skipping 301 matching lines @@
   ColorMap::const_iterator it = colors_.find(id);
   if (it != colors_.end()) {
     *color = it->second;
     return true;
   }
 
   return false;
 }
 
 ui::NativeTheme* Gtk2UI::GetNativeTheme() const {
-  return NULL;
+  return NativeThemeGtk2::instance();
 }
 
 ui::SelectFileDialog* Gtk2UI::CreateSelectFileDialog(
     ui::SelectFileDialog::Listener* listener,
     ui::SelectFilePolicy* policy) const {
   return SelectFileDialogImpl::Create(listener, policy);
 }
 
 void Gtk2UI::GetScrollbarColors(GdkColor* thumb_active_color,
                                 GdkColor* thumb_inactive_color,
@@ skipping 624 matching lines @@
 
 void Gtk2UI::ClearAllThemeData() {
   STLDeleteValues(&gtk_images_);
 }
 
 }  // namespace libgtk2ui
 
 ui::LinuxUI* BuildGtk2UI() {
   return new libgtk2ui::Gtk2UI;
 }