MouseWheelEventManager is added to handle wheel events.

third_party/WebKit/Source/core/input/EventHandler.h

 /*
  * Copyright (C) 2006, 2007, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 
 #ifndef EventHandler_h
 #define EventHandler_h
 
 #include "core/CoreExport.h"
 #include "core/dom/UserGestureIndicator.h"
 #include "core/events/TextEventInputType.h"
 #include "core/input/GestureManager.h"
 #include "core/input/KeyboardEventManager.h"
 #include "core/input/MouseEventManager.h"
+#include "core/input/MouseWheelEventManager.h"
 #include "core/input/PointerEventManager.h"
 #include "core/input/ScrollManager.h"
 #include "core/layout/HitTestRequest.h"
 #include "core/page/DragActions.h"
 #include "core/page/EventWithHitTestResults.h"
 #include "core/style/ComputedStyleConstants.h"
 #include "platform/Cursor.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollTypes.h"
@@ skipping 320 matching lines @@
 
   Member<Node> drag_target_;
   bool should_only_fire_drag_over_event_;
 
   Member<HTMLFrameSetElement> frame_set_being_resized_;
 
   RefPtr<UserGestureToken> last_mouse_down_user_gesture_token_;
 
   Member<ScrollManager> scroll_manager_;
   Member<MouseEventManager> mouse_event_manager_;
+  Member<MouseWheelEventManager> mouse_wheel_event_manager_;
   Member<KeyboardEventManager> keyboard_event_manager_;
   Member<PointerEventManager> pointer_event_manager_;
   Member<GestureManager> gesture_manager_;
 
   double max_mouse_moved_duration_;
 
   bool long_tap_should_invoke_context_menu_;
 
   TaskRunnerTimer<EventHandler> active_interval_timer_;
   double last_show_press_timestamp_;
   Member<Element> last_deferred_tap_element_;
 
   // Set on GestureTapDown if the |pointerdown| event corresponding to the
   // triggering |touchstart| event was canceled. This suppresses mouse event
   // firing for the current gesture sequence (i.e. until next GestureTapDown).
   bool suppress_mouse_events_from_gestures_;
 };
 
 }  // namespace blink
 
 #endif  // EventHandler_h