Implement MouseEvent buttons attribute.

Source/core/events/MouseEvent.h

 /*
  * 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, 2004, 2005, 2006, 2008 Apple Inc. 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 27 matching lines @@
 
     int screenX;
     int screenY;
     int clientX;
     int clientY;
     bool ctrlKey;
     bool altKey;
     bool shiftKey;
     bool metaKey;
     unsigned short button;
+    unsigned short buttons;
     RefPtrWillBeMember<EventTarget> relatedTarget;
 };
 
 class MouseEvent : public MouseRelatedEvent {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<MouseEvent> create()
     {
         return adoptRefWillBeNoop(new MouseEvent);
     }
 
     static PassRefPtrWillBeRawPtr<MouseEvent> create(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtrWillBeRawPtr<AbstractView>,
         int detail, int screenX, int screenY, int pageX, int pageY,
         int movementX, int movementY,
-        bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short button,
+        bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short button, unsigned short buttons,
         PassRefPtrWillBeRawPtr<EventTarget> relatedTarget, PassRefPtrWillBeRawPtr<DataTransfer>,
         bool isSimulated = false, PlatformMouseEvent::SyntheticEventType = PlatformMouseEvent::RealOrIndistinguishable);
 
     static PassRefPtrWillBeRawPtr<MouseEvent> create(const AtomicString& eventType, PassRefPtrWillBeRawPtr<AbstractView>, const PlatformMouseEvent&, int detail, PassRefPtrWillBeRawPtr<Node> relatedTarget);
 
     static PassRefPtrWillBeRawPtr<MouseEvent> create(const AtomicString& eventType, const MouseEventInit&);
 
     virtual ~MouseEvent();
 
     void initMouseEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtrWillBeRawPtr<AbstractView>,
         int detail, int screenX, int screenY, int clientX, int clientY,
         bool ctrlKey, bool altKey, bool shiftKey, bool metaKey,
-        unsigned short button, PassRefPtrWillBeRawPtr<EventTarget> relatedTarget);
+        unsigned short button, PassRefPtrWillBeRawPtr<EventTarget> relatedTarget, unsigned short buttons = 0);
 
     // WinIE uses 1,4,2 for left/middle/right but not for click (just for mousedown/up, maybe others),
     // but we will match the standard DOM.
     unsigned short button() const { return m_button; }
+    unsigned short buttons() const { return m_buttons; }
     bool buttonDown() const { return m_buttonDown; }
     EventTarget* relatedTarget() const { return m_relatedTarget.get(); }
     void setRelatedTarget(PassRefPtrWillBeRawPtr<EventTarget> relatedTarget) { m_relatedTarget = relatedTarget; }
 
     Node* toElement() const;
     Node* fromElement() const;
 
     DataTransfer* dataTransfer() const { return isDragEvent() ? m_dataTransfer.get() : 0; }
 
     bool fromTouch() const { return m_syntheticEventType == PlatformMouseEvent::FromTouch; }
 
     virtual const AtomicString& interfaceName() const override;
 
     virtual bool isMouseEvent() const override;
     virtual bool isDragEvent() const override final;
     virtual int which() const override final;
 
     virtual void trace(Visitor*) override;
 
 protected:
     MouseEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtrWillBeRawPtr<AbstractView>,
         int detail, int screenX, int screenY, int pageX, int pageY,
         int movementX, int movementY,
-        bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short button,
+        bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, unsigned short button, unsigned short buttons,
         PassRefPtrWillBeRawPtr<EventTarget> relatedTarget, PassRefPtrWillBeRawPtr<DataTransfer>,
         bool isSimulated, PlatformMouseEvent::SyntheticEventType);
 
     MouseEvent(const AtomicString& type, const MouseEventInit&);
 
     MouseEvent();
 
 private:
     unsigned short m_button;
+    unsigned short m_buttons;
     bool m_buttonDown;
     RefPtrWillBeMember<EventTarget> m_relatedTarget;
     RefPtrWillBeMember<DataTransfer> m_dataTransfer;
     PlatformMouseEvent::SyntheticEventType m_syntheticEventType;
 };
 
 class SimulatedMouseEvent final : public MouseEvent {
 public:
     static PassRefPtrWillBeRawPtr<SimulatedMouseEvent> create(const AtomicString& eventType, PassRefPtrWillBeRawPtr<AbstractView>, PassRefPtrWillBeRawPtr<Event> underlyingEvent);
     virtual ~SimulatedMouseEvent();
@@ skipping 16 matching lines @@
     virtual bool dispatchEvent(EventDispatcher*) const override;
     bool isSyntheticMouseEvent() const { return m_mouseEventType == SyntheticMouseEvent; }
     MouseEventType m_mouseEventType;
 };
 
 DEFINE_EVENT_TYPE_CASTS(MouseEvent);
 
 } // namespace blink
 
 #endif // MouseEvent_h