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

Source/core/events/TextEvent.h

Index: Source/core/events/TextEvent.h
diff --git a/Source/core/events/TextEvent.h b/Source/core/events/TextEvent.h
index 782ed0d0090b3dc9be40d93db898ee1dd5750ab1..cbb0afbb77ec381670c20bdaf3f3935164634fa0 100644
--- a/Source/core/events/TextEvent.h
+++ b/Source/core/events/TextEvent.h
@@ -61,6 +61,8 @@ namespace WebCore {
         bool shouldMatchStyle() const { return m_shouldMatchStyle; }
         DocumentFragment* pastingFragment() const { return m_pastingFragment.get(); }
 
+        virtual void trace(Visitor*) OVERRIDE;
+
     private:
         TextEvent();