Oilpan: add transition types to track interface objects.

Source/core/html/track/TrackBase.h

Index: Source/core/html/track/TrackBase.h
diff --git a/Source/core/html/track/TrackBase.h b/Source/core/html/track/TrackBase.h
index b291c68db363fd0a7b2e59c5c97e2c86a39aa651..d3625f076e5d349e4e089b20a86f5ba9e4c8b9c5 100644
--- a/Source/core/html/track/TrackBase.h
+++ b/Source/core/html/track/TrackBase.h
@@ -26,12 +26,13 @@
 #ifndef TrackBase_h
 #define TrackBase_h
 
+#include "platform/heap/Handle.h"
 #include "wtf/RefCounted.h"
 #include "wtf/text/AtomicString.h"
 
 namespace WebCore {
 
-class TrackBase : public RefCounted<TrackBase> {
+class TrackBase : public RefCountedWillBeRefCountedGarbageCollected<TrackBase> {
 public:
     virtual ~TrackBase();
 
@@ -50,6 +51,8 @@ public:
     AtomicString id() const { return m_id; }
     void setId(const AtomicString& id) { m_id = id; }
 
+    virtual void trace(Visitor*) { }
+
 protected:
     TrackBase(Type, const AtomicString& label, const AtomicString& language, const AtomicString& id);