Reland: Reland: Implement new Blink IDL attribute [SetReference]

Source/bindings/v8/UnsafePersistent.h

 /*
  * Copyright (C) 2013 Google Inc. 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
@@ skipping 70 matching lines @@
     }
 
     // This is incredibly unsafe: the handle is valid only when this
     // UnsafePersistent is alive and valid (see class level comment).
     v8::Persistent<T>* persistent()
     {
         v8::Persistent<T>* handle = reinterpret_cast<v8::Persistent<T>*>(&m_value);
         return handle;
     }
 
+    void setReferenceFrom(const v8::Persistent<v8::Object>& parent, v8::Isolate* isolate)
+    {
+        isolate->SetReference(parent, *persistent());
+    }
+
     void dispose()
     {
         persistent()->Dispose();
         m_value = 0;
     }
 
     void clear()
     {
         m_value = 0;
     }
@@ skipping 14 matching lines @@
         v8::Handle<T>* handle = reinterpret_cast<v8::Handle<T>*>(&m_value);
         return *handle;
     }
 
     T* m_value;
 };
 
 } // namespace WebCore
 
 #endif // UnsafePersistent_h