chrome: Cleanup class/struct forward declarations

chrome/browser/ui/libgtkui/gtk_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_LIBGTKUI_GTK_UI_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_GTK_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/libgtkui/gtk_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 libgtkui {
 class Gtk2KeyBindingsHandler;
 class GConfListener;
 
 // Interface to GTK2 desktop features.
 //
 class Gtk2UI : public views::LinuxUI {
  public:
   Gtk2UI();
   ~Gtk2UI() override;
@@ skipping 173 matching lines @@
 }  // 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.
 LIBGTKUI_EXPORT views::LinuxUI* BuildGtk2UI();
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_GTK_UI_H_