Canvas2d: Implement rerouting event by hit region's control.

third_party/WebKit/Source/core/events/WheelEvent.cpp

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Samsung Electronics. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 58 matching lines @@
     , m_railsMode(RailsModeFree)
 {
 }
 
 WheelEvent::WheelEvent(const FloatPoint& wheelTicks, const FloatPoint& rawDelta, unsigned deltaMode,
     PassRefPtrWillBeRawPtr<AbstractView> view, const IntPoint& screenLocation, const IntPoint& windowLocation,
     PlatformEvent::Modifiers modifiers, unsigned short buttons, double platformTimeStamp,
     bool canScroll, int resendingPluginId, bool hasPreciseScrollingDeltas, RailsMode railsMode)
     : MouseEvent(EventTypeNames::wheel, true, true, view, 0, screenLocation.x(), screenLocation.y(),
         windowLocation.x(), windowLocation.y(), 0, 0, modifiers, 0, buttons,
-        nullptr, platformTimeStamp, PlatformMouseEvent::RealOrIndistinguishable)
+        nullptr, platformTimeStamp, PlatformMouseEvent::RealOrIndistinguishable,
+        // TODO(zino): Should support canvas hit region because the wheel event
+        // is a kind of mouse event. Please see http://crbug.com/594075
+        String())
     , m_wheelDelta(wheelTicks.x() * TickMultiplier, wheelTicks.y() * TickMultiplier)
     , m_deltaX(-rawDelta.x())
     , m_deltaY(-rawDelta.y())
     , m_deltaZ(0)
     , m_deltaMode(deltaMode)
     , m_canScroll(canScroll)
     , m_resendingPluginId(resendingPluginId)
     , m_hasPreciseScrollingDeltas(hasPreciseScrollingDeltas)
     , m_railsMode(railsMode)
 {
@@ skipping 18 matching lines @@
 {
     return EventDispatchMediator::create(this);
 }
 
 DEFINE_TRACE(WheelEvent)
 {
     MouseEvent::trace(visitor);
 }
 
 } // namespace blink