Revert Event back (from RefCountedWillBeRefCountedGarbageCollected) to RefCounted

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 77ba12b5925633c13c7db131ecd8ba19c43bcbe6..3783fa6a98e34948a74ce217a149398a9637b54d 100644
--- a/Source/core/events/MouseEvent.h
+++ b/Source/core/events/MouseEvent.h
@@ -91,6 +91,8 @@ public:
     virtual bool isDragEvent() const OVERRIDE FINAL;
     virtual int which() const OVERRIDE FINAL;
 
+    virtual void trace(Visitor*) OVERRIDE;
+
 protected:
     MouseEvent(const AtomicString& type, bool canBubble, bool cancelable, PassRefPtr<AbstractView>,
         int detail, int screenX, int screenY, int pageX, int pageY,
@@ -102,8 +104,6 @@ protected:
 
     MouseEvent();
 
-    virtual void trace(Visitor*) OVERRIDE;
-
 private:
     unsigned short m_button;
     bool m_buttonDown;