Add ScriptValue.v8ValueUnsafe() to access the V8 value without cross-context access check.

Source/bindings/core/v8/ScriptValue.h

 /*
  * Copyright (C) 2008, 2009 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 129 matching lines @@
     {
         return !m_value.get() || m_value->isEmpty();
     }
 
     void clear()
     {
         m_value = nullptr;
     }
 
     v8::Handle<v8::Value> v8Value() const;
+    v8::Handle<v8::Value> v8ValueUnsafe() const;
 
     bool toString(String&) const;
     PassRefPtr<JSONValue> toJSONValue(ScriptState*) const;
 
 private:
     mutable v8::Isolate* m_isolate;
     mutable RefPtr<ScriptState> m_scriptState;
     RefPtr<SharedPersistent<v8::Value> > m_value;
 };
 
 } // namespace blink
 
 #endif // ScriptValue_h