chrome: Cleanup class/struct forward declarations

chrome/browser/ui/libgtkui/gtk_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_LIBGTKUI_GTK_UTIL_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_GTK_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 {
@@ skipping 24 matching lines @@
 
 // Gets the transient parent aura window for |dialog|.
 aura::Window* GetAuraTransientParent(GtkWidget* dialog);
 
 // Clears the transient parent for |dialog|.
 void ClearAuraTransientParent(GtkWidget* dialog);
 
 }  // namespace libgtkui
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK_UTIL_H_