Reduce platform/heap/ wtf includes.

Source/wtf/Forward.h

 /*
  *  Copyright (C) 2006, 2009, 2011 Apple 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,
  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 12 matching lines @@
 
 #include <stddef.h>
 
 namespace WTF {
     template<typename T> class Function;
     template<typename T> class OwnPtr;
     template<typename T> class PassOwnPtr;
     template<typename T> class PassRefPtr;
     template<typename T> class RefPtr;
     template<typename T, size_t inlineCapacity, typename Allocator> class Vector;
+    template<typename T> class WeakPtr;
 
     class ArrayBuffer;
     class ArrayBufferView;
     class ArrayPiece;
     class AtomicString;
     class CString;
     class Float32Array;
     class Float64Array;
     class Int8Array;
     class Int16Array;
     class Int32Array;
     template<size_t size>
     class SizeSpecificPartitionAllocator;
     class String;
     template <typename T> class StringBuffer;
     class StringBuilder;
     class StringImpl;
     class Uint8Array;
     class Uint8ClampedArray;
     class Uint16Array;
     class Uint32Array;
 }
 
 using WTF::Function;
 using WTF::OwnPtr;
 using WTF::PassOwnPtr;
 using WTF::PassRefPtr;
 using WTF::RefPtr;
 using WTF::Vector;
+using WTF::WeakPtr;
 
 using WTF::ArrayBuffer;
 using WTF::ArrayBufferView;
 using WTF::ArrayPiece;
 using WTF::AtomicString;
 using WTF::CString;
 using WTF::Float32Array;
 using WTF::Float64Array;
 using WTF::Int8Array;
 using WTF::Int16Array;
 using WTF::Int32Array;
 using WTF::String;
 using WTF::StringBuffer;
 using WTF::StringBuilder;
 using WTF::StringImpl;
 using WTF::Uint8Array;
 using WTF::Uint8ClampedArray;
 using WTF::Uint16Array;
 using WTF::Uint32Array;
 
 #endif // WTF_Forward_h