[api] Prototype WeakRef implementation

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 2148 matching lines @@
    * Returns true if this value is a WeakMap.
    */
   bool IsWeakMap() const;
 
   /**
    * Returns true if this value is a WeakSet.
    */
   bool IsWeakSet() const;
 
   /**
+   * Returns true if this value is a WeakRef.
+   */
+  bool IsWeakRef() const;
+
+  /**
    * Returns true if this value is an ArrayBuffer.
    */
   bool IsArrayBuffer() const;
 
   /**
    * Returns true if this value is an ArrayBufferView.
    */
   bool IsArrayBufferView() const;
 
   /**
@@ skipping 7893 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_