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

Source/modules/device_orientation/DeviceOrientationEvent.cpp

 /*
  * Copyright 2010, The Android Open Source Project
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *  * Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 80 matching lines @@
 
     isNull = true;
     return 0;
 }
 
 const AtomicString& DeviceOrientationEvent::interfaceName() const
 {
     return EventNames::DeviceOrientationEvent;
 }
 
+void DeviceOrientationEvent::trace(Visitor* visitor)
+{
+    visitor->trace(m_orientation);
+    Event::trace(visitor);
+}
+
 } // namespace WebCore