ui: Cleanup class/struct forward declarations

ui/views/corewm/tooltip_aura.h

 // Copyright 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 UI_VIEWS_COREWM_TOOLTIP_AURA_H_
 #define UI_VIEWS_COREWM_TOOLTIP_AURA_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/views/corewm/tooltip.h"
 #include "ui/views/widget/widget_observer.h"
 
 namespace gfx {
-class FontList;
 class Size;
 }  // namespace gfx
 
 namespace views {
 
 class Widget;
 
 namespace corewm {
 
 // Implementation of Tooltip that shows the tooltip using a Widget and Label.
@@ skipping 35 matching lines @@
   // showing.
   aura::Window* tooltip_window_;
 
   DISALLOW_COPY_AND_ASSIGN(TooltipAura);
 };
 
 }  // namespace corewm
 }  // namespace views
 
 #endif  // UI_VIEWS_COREWM_TOOLTIP_AURA_H_