Remove more bits of the Oilpan tracing system

sky/engine/wtf/HashSet.h

Index: sky/engine/wtf/HashSet.h
diff --git a/sky/engine/wtf/HashSet.h b/sky/engine/wtf/HashSet.h
index 55a6e5d88a0f42a9199b084ff433b523bf3a8f75..fe0e1e51333eba405efbb0889b2fed40d8a2a72d 100644
--- a/sky/engine/wtf/HashSet.h
+++ b/sky/engine/wtf/HashSet.h
@@ -108,8 +108,6 @@ namespace WTF {
         ValuePassOutType take(ValuePeekInType);
         ValuePassOutType takeAny();
 
-        void trace(typename Allocator::Visitor* visitor) { m_impl.trace(visitor); }
-
     private:
         HashTableType m_impl;
     };
@@ -272,13 +270,6 @@ namespace WTF {
             vector[i] = *it;
     }
 
-#if !ENABLE(OILPAN)
-    template<typename T, typename U, typename V>
-    struct NeedsTracing<HashSet<T, U, V> > {
-        static const bool value = false;
-    };
-#endif
-
 } // namespace WTF
 
 using WTF::HashSet;