Remove more bits of the Oilpan tracing system

sky/engine/wtf/HashCountedSet.h

Index: sky/engine/wtf/HashCountedSet.h
diff --git a/sky/engine/wtf/HashCountedSet.h b/sky/engine/wtf/HashCountedSet.h
index 79b3fefadc90a2d25c96961989b65a7dd3d5964e..1b6456bec5c6ae3b1a36d8bcddad815423eaef3e 100644
--- a/sky/engine/wtf/HashCountedSet.h
+++ b/sky/engine/wtf/HashCountedSet.h
@@ -80,8 +80,6 @@ namespace WTF {
         // Clears the whole set.
         void clear() { m_impl.clear(); }
 
-        void trace(typename Allocator::Visitor* visitor) { m_impl.trace(visitor); }
-
     private:
         ImplType m_impl;
     };
@@ -147,13 +145,6 @@ namespace WTF {
             vector[i] = (*it).key;
     }
 
-#if !ENABLE(OILPAN)
-    template<typename T, typename U, typename V>
-    struct NeedsTracing<HashCountedSet<T, U, V> > {
-        static const bool value = false;
-    };
-#endif
-
 } // namespace WTF
 
 using WTF::HashCountedSet;