Populates sourceDevice attribute into MouseEvent

Source/core/events/MouseEvent.h

Index: Source/core/events/MouseEvent.h
diff --git a/Source/core/events/MouseEvent.h b/Source/core/events/MouseEvent.h
index 7914547c960ca2aa471d2535115b0efe583cbfb7..85021457e3eb5bb16e4f71dc1ffc4f19eb02f75e 100644
--- a/Source/core/events/MouseEvent.h
+++ b/Source/core/events/MouseEvent.h
@@ -64,6 +64,11 @@ public:
         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; }