Write a NativeThemeGtk2 class for linux_aura.

chrome/browser/ui/libgtk2ui/native_theme_gtk2.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_NATIVE_THEME_GTK2_H_
+#define CHROME_BROWSER_UI_LIBGTK2UI_NATIVE_THEME_GTK2_H_
+
+#include "chrome/browser/ui/libgtk2ui/owned_widget_gtk2.h"
+#include "ui/native_theme/native_theme_base.h"
+
+typedef struct _GdkColor GdkColor;
+typedef struct _GtkStyle GtkStyle;
+typedef struct _GtkWidget GtkWidget;
+
+namespace libgtk2ui {
+
+// A version of NativeTheme that uses GTK2 supplied colours instead of the
+// default aura colours. Analogue to NativeThemeWin, except that can't be
+// compiled into the main chrome binary like the Windows code can.
+class NativeThemeGtk2 : public ui::NativeThemeBase {
+ public:
+  static NativeThemeGtk2* instance();
+
+  // Overridden from ui::NativeThemeBase:
+  virtual SkColor GetSystemColor(ColorId color_id) const OVERRIDE;
+  virtual void PaintMenuPopupBackground(
+      SkCanvas* canvas,
+      const gfx::Size& size,
+      const MenuBackgroundExtraParams& menu_background) const OVERRIDE;
+
+ private:
+  NativeThemeGtk2();
+  virtual ~NativeThemeGtk2();
+
+  // Implementation of GetSystemColor.
+  GdkColor GetSystemGdkColor(ColorId color_id) const;
+
+  // Returns styles associated with various widget types.
+  GtkWidget* GetRealizedWindow() const;
+  GtkStyle* GetWindowStyle() const;
+  GtkStyle* GetEntryStyle() const;
+  GtkStyle* GetLabelStyle() const;
+  GtkStyle* GetButtonStyle() const;
+  GtkStyle* GetMenuStyle() const;
+  GtkStyle* GetMenuItemStyle() const;
+
+  mutable GtkWidget* fake_window_;

[sky, 2013/03/05 03:59:03]

How come this one can't be an OwnedWidgetGtk too?

+  mutable OwnedWidgetGtk fake_entry_;
+  mutable OwnedWidgetGtk fake_label_;
+  mutable OwnedWidgetGtk fake_button_;
+
+  mutable OwnedWidgetGtk fake_menu_;
+  mutable GtkWidget* fake_menu_item_;
+
+  DISALLOW_COPY_AND_ASSIGN(NativeThemeGtk2);
+};
+
+}  // namespace libgtk2ui
+
+#endif  // CHROME_BROWSER_UI_LIBGTK2UI_NATIVE_THEME_GTK2_H_