Populates sourceDevice attribute into MouseEvent

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 46 matching lines @@
 
     virtual ~MouseEvent();
 
     static unsigned short platformModifiersToButtons(unsigned modifiers);
 
     void initMouseEvent(ScriptState*, 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,
         short button, PassRefPtrWillBeRawPtr<EventTarget> relatedTarget, unsigned short buttons = 0);
 
+    void initMouseEvent(ScriptState*, 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,
+        short button, PassRefPtrWillBeRawPtr<EventTarget> relatedTarget, InputDevice* sourceDevice, unsigned short buttons = 0);

[Rick Byers, 2015/06/23 00:55:57]

Do you really need to add a new overload or could you just rely on a default
value (sourceDevice = 0)?

[lanwei, 2015/06/23 22:19:20]

Done.

+
     // 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.
     short button() const { return m_button == -1 ? 0 : m_button; }
     unsigned short buttons() const { return m_buttons; }
     bool buttonDown() const { return m_button != -1; }
     EventTarget* relatedTarget() const { return m_relatedTarget.get(); }
     void setRelatedTarget(PassRefPtrWillBeRawPtr<EventTarget> relatedTarget) { m_relatedTarget = relatedTarget; }
 
     Node* toElement() const;
     Node* fromElement() const;
@@ skipping 53 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