ui: Cleanup class/struct forward declarations

ui/ozone/public/system_input_injector.h

 // Copyright 2014 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_OZONE_PUBLIC_SYSTEM_INPUT_INJECTOR_H_
 #define UI_OZONE_PUBLIC_SYSTEM_INPUT_INJECTOR_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "ui/events/event.h"
 #include "ui/events/keycodes/dom/keycode_converter.h"
 #include "ui/gfx/geometry/point_f.h"
 #include "ui/ozone/ozone_export.h"
 
 namespace gfx {
 class PointF;
 }  // namespace gfx
 
 namespace ui {
-class Event;
 
 // Interface for converting input into ui::Events and injecting them to the
 // Ozone platform.
 class OZONE_EXPORT SystemInputInjector {
  public:
   SystemInputInjector() {}
   virtual ~SystemInputInjector() {}
 
   // Moves the cursor on the screen and generates the corresponding MouseMove or
   // MouseDragged event.  |location| is in physical screen coordinates,
@@ skipping 17 matching lines @@
                               bool down,
                               bool suppress_auto_repeat) = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SystemInputInjector);
 };
 
 }  // namespace ui
 
 #endif  // UI_OZONE_PUBLIC_SYSTEM_INPUT_INJECTOR_H_