Implement MouseEvent buttons attribute.

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 42 matching lines @@
     , m_wheelDelta(initializer.wheelDeltaX ? initializer.wheelDeltaX : -initializer.deltaX, initializer.wheelDeltaY ? initializer.wheelDeltaY : -initializer.deltaY)
     , m_deltaX(initializer.deltaX ? initializer.deltaX : -initializer.wheelDeltaX)
     , m_deltaY(initializer.deltaY ? initializer.deltaY : -initializer.wheelDeltaY)
     , m_deltaZ(initializer.deltaZ)
     , m_deltaMode(initializer.deltaMode)
 {
 }
 
 WheelEvent::WheelEvent(const FloatPoint& wheelTicks, const FloatPoint& rawDelta, unsigned deltaMode,
     PassRefPtrWillBeRawPtr<AbstractView> view, const IntPoint& screenLocation, const IntPoint& pageLocation,
-    bool ctrlKey, bool altKey, bool shiftKey, bool metaKey)
+    bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short buttons)
     : MouseEvent(EventTypeNames::wheel, true, true, view, 0, screenLocation.x(), screenLocation.y(),
-        pageLocation.x(), pageLocation.y(), 0, 0, ctrlKey, altKey, shiftKey, metaKey, 0, nullptr,
-        nullptr, false, PlatformMouseEvent::RealOrIndistinguishable)
+        pageLocation.x(), pageLocation.y(), 0, 0, ctrlKey, altKey, shiftKey, metaKey, 0, buttons,
+        nullptr, nullptr, false, PlatformMouseEvent::RealOrIndistinguishable)
     , m_wheelDelta(wheelTicks.x() * TickMultiplier, wheelTicks.y() * TickMultiplier)
     , m_deltaX(-rawDelta.x())
     , m_deltaY(-rawDelta.y())
     , m_deltaZ(0)
     , m_deltaMode(deltaMode)
 {
 }
 
 const AtomicString& WheelEvent::interfaceName() const
 {
@@ skipping 25 matching lines @@
     return adoptRefWillBeNoop(new WheelEventDispatchMediator(event, view));
 }
 
 WheelEventDispatchMediator::WheelEventDispatchMediator(const PlatformWheelEvent& event, PassRefPtrWillBeRawPtr<AbstractView> view)
 {
     if (!(event.deltaX() || event.deltaY()))
         return;
 
     setEvent(WheelEvent::create(FloatPoint(event.wheelTicksX(), event.wheelTicksY()), FloatPoint(event.deltaX(), event.deltaY()),
         deltaMode(event), view, event.globalPosition(), event.position(),
-        event.ctrlKey(), event.altKey(), event.shiftKey(), event.metaKey()));
+        event.ctrlKey(), event.altKey(), event.shiftKey(), event.metaKey(),
+        MouseEvent::platformModifiersToButtons(event.modifiers())));
 }
 
 WheelEvent* WheelEventDispatchMediator::event() const
 {
     return toWheelEvent(EventDispatchMediator::event());
 }
 
 bool WheelEventDispatchMediator::dispatchEvent(EventDispatcher* dispatcher) const
 {
     ASSERT(event());
     return EventDispatchMediator::dispatchEvent(dispatcher) && !event()->defaultHandled();
 }
 
 } // namespace blink