Make sure all destructors are called in HeapHashMap and HeapHashSet

Source/wtf/TypeTraits.h

  /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 288 matching lines @@
     template<typename V> static NoType checkHasTraceMethod(...);
 public:
     static const bool value = sizeof(YesType) == sizeof(checkHasTraceMethod<T>(0));
 };
 
 // Convenience template wrapping the NeedsTracingLazily template in
 // Collection Traits. It helps make the code more readable.
 template<typename Traits>
 class ShouldBeTraced {
 public:
-    static const bool value = Traits::template NeedsTracingLazily<void>::value;
+    static const bool value = Traits::template NeedsTracingLazily<>::value;
 };
 
 } // namespace WTF
 
 #endif // TypeTraits_h