Populates sourceDevice attribute into TouchEvent

Source/core/events/TouchEvent.cpp

Index: Source/core/events/TouchEvent.cpp
diff --git a/Source/core/events/TouchEvent.cpp b/Source/core/events/TouchEvent.cpp
index d064db1a6c98436166495eda847ca5629a784b4a..80e21b5a95d97dfaca459eae8269fd889e36cbc3 100644
--- a/Source/core/events/TouchEvent.cpp
+++ b/Source/core/events/TouchEvent.cpp
@@ -46,8 +46,8 @@ TouchEvent::TouchEvent(TouchList* touches, TouchList* targetTouches,
         PassRefPtrWillBeRawPtr<AbstractView> view,
         bool ctrlKey, bool altKey, bool shiftKey, bool metaKey, bool cancelable, bool causesScrollingIfUncanceled,
         double uiCreateTime)
-    : UIEventWithKeyState(type, true, cancelable, view, 0,
-                        ctrlKey, altKey, shiftKey, metaKey)
+    // Pass a sourceDevice which fires touchevents to UIEventWithKeyState when creating touchevent.
+    : UIEventWithKeyState(type, true, cancelable, view, 0, ctrlKey, altKey, shiftKey, metaKey, InputDevice::touchEventInstance())

[tdresser, 2015/06/10 13:46:00]

This comment doesn't make it clear why we're assuming that this event is being
created by user input.

[lanwei, 2015/06/10 23:23:22]

Done.

     , m_touches(touches)
     , m_targetTouches(targetTouches)
     , m_changedTouches(changedTouches)