Populates sourceDevice attribute into TouchEvent

Source/core/events/UIEvent.cpp

Index: Source/core/events/UIEvent.cpp
diff --git a/Source/core/events/UIEvent.cpp b/Source/core/events/UIEvent.cpp
index 3e563d6e067870d7fc68ccb22e1d3d76755a6cdd..7ec400e78f1de72f1d93e1205ad904e35e69bd1a 100644
--- a/Source/core/events/UIEvent.cpp
+++ b/Source/core/events/UIEvent.cpp
@@ -32,11 +32,12 @@ UIEvent::UIEvent()
 {
 }
 
-UIEvent::UIEvent(const AtomicString& eventType, bool canBubbleArg, bool cancelableArg, PassRefPtrWillBeRawPtr<AbstractView> viewArg, int detailArg)
+// TODO(lanwei): Will add sourceDevice to all the subclass of UIEvent later, see https://crbug.com/476530.
+UIEvent::UIEvent(const AtomicString& eventType, bool canBubbleArg, bool cancelableArg, PassRefPtrWillBeRawPtr<AbstractView> viewArg, int detailArg, InputDevice* sourceDeviceArg)
     : Event(eventType, canBubbleArg, cancelableArg)
     , m_view(viewArg)
     , m_detail(detailArg)
-    , m_sourceDevice(nullptr)
+    , m_sourceDevice(sourceDeviceArg)
 {
 }