[api] Add an API function to set the GetExternallyAllocatedMemoryInBytesCallback.

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 7129 matching lines @@
    */
   void AddGCEpilogueCallback(GCCallback callback,
                              GCType gc_type_filter = kGCTypeAll);
 
   /**
    * This function removes callback which was installed by
    * AddGCEpilogueCallback function.
    */
   void RemoveGCEpilogueCallback(GCCallback callback);
 
+  typedef size_t (*GetExternallyAllocatedMemoryInBytesCallback)();
+
+  /**
+   * Set the callback that tells V8 how much memory is currently allocated
+   * externally of the V8 heap. Ideally this memory is somehow connected to V8
+   * objects and may get freed-up when the corresponding V8 objects get
+   * collected by a V8 garbage collection.
+   */
+  void SetGetExternallyAllocatedMemoryInBytesCallback(
+      GetExternallyAllocatedMemoryInBytesCallback callback);
+
   /**
    * Forcefully terminate the current thread of JavaScript execution
    * in the given isolate.
    *
    * This method can be used by any thread even if that thread has not
    * acquired the V8 lock with a Locker object.
    */
   void TerminateExecution();
 
   /**
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  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_