Make Event RefCountedGarbageCollected and implement trace() methods to the Event hierarcy

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 68d80957cd2188da90e69d2af15a6cedf496c1f0..cd7f311cc0b2a5dd3d62ae9935221b7a6bf20495 100644
--- a/Source/core/events/TouchEvent.cpp
+++ b/Source/core/events/TouchEvent.cpp
@@ -88,6 +88,11 @@ bool TouchEvent::isTouchEvent() const
     return true;
 }
 
+void TouchEvent::trace(Visitor* visitor)
+{
+    MouseRelatedEvent::trace(visitor);
+}
+
 PassRefPtr<TouchEventDispatchMediator> TouchEventDispatchMediator::create(PassRefPtr<TouchEvent> touchEvent)
 {
     return adoptRef(new TouchEventDispatchMediator(touchEvent));