move CopyablePersistentTraits to v8.h

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 462 matching lines @@
     Uncompilable<Object>();
   }
   // TODO(dcarney): come up with a good compile error here.
   template<class O> V8_INLINE static void Uncompilable() {
     TYPE_CHECK(O, Primitive);
   }
 };
 
 
 /**
+ * Helper class traits to allow copying and assignment of Persistent.
+ * This will clone the contents of storage cell, but not any of the flags, etc.
+ */
+template<class T>
+struct CopyablePersistentTraits {
+  typedef Persistent<T, CopyablePersistentTraits<T> > CopyablePersistent;
+  static const bool kResetInDestructor = true;
+  template<class S, class M>
+  static V8_INLINE void Copy(const Persistent<S, M>& source,
+                             CopyablePersistent* dest) {
+    // do nothing, just allow copy
+  }
+};
+
+
+/**
  * An object reference that is independent of any handle scope.  Where
  * a Local handle only lives as long as the HandleScope in which it was
  * allocated, a Persistent handle remains valid until it is explicitly
  * disposed.
  *
  * A persistent handle contains a reference to a storage cell within
  * the v8 engine which holds an object value and which is updated by
  * the garbage collector whenever the object is moved.  A new storage
  * cell can be created using the constructor or Persistent::Reset and
  * existing handles can be disposed using Persistent::Reset.
@@ skipping 5962 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_