Remove more bits of the Oilpan tracing system

sky/engine/wtf/HashMap.h

Index: sky/engine/wtf/HashMap.h
diff --git a/sky/engine/wtf/HashMap.h b/sky/engine/wtf/HashMap.h
index 021a1e67802d82abc03475f3c6f8c26eb348229b..d6d2c7b6f7b268d8cbd002c80750bf1c63fd930a 100644
--- a/sky/engine/wtf/HashMap.h
+++ b/sky/engine/wtf/HashMap.h
@@ -153,8 +153,6 @@ namespace WTF {
 
         static bool isValidKey(KeyPeekInType);
 
-        void trace(typename Allocator::Visitor* visitor) { m_impl.trace(visitor); }
-
     private:
         AddResult inlineAdd(KeyPassInType, MappedPassInReferenceType);
 
@@ -493,13 +491,6 @@ namespace WTF {
             vector[i] = *it;
     }
 
-#if !ENABLE(OILPAN)
-template<typename T, typename U, typename V, typename W, typename X>
-struct NeedsTracing<HashMap<T, U, V, W, X> > {
-    static const bool value = false;
-};
-#endif
-
 } // namespace WTF
 
 using WTF::HashMap;