Add an ASSERT about cross-world wrapper leakage into ScriptValue

Source/bindings/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 39 matching lines @@
     {
     }
 
     virtual ~ScriptValue();
 
     ScriptValue(ScriptState* scriptState, v8::Handle<v8::Value> value)
         : m_isolate(scriptState->isolate())
         , m_scriptState(scriptState)
         , m_value(value.IsEmpty() ? nullptr : SharedPersistent<v8::Value>::create(value, scriptState->isolate()))
     {
+        ASSERT(isEmpty() || m_scriptState);
     }
 
     ScriptValue(const ScriptValue& value)
         : m_isolate(value.m_isolate)
         , m_scriptState(value.m_scriptState)
         , m_value(value.m_value)
     {
+        ASSERT(isEmpty() || m_scriptState);
     }
 
     ScriptState* scriptState() const
     {
         return m_scriptState.get();
     }
 
     v8::Isolate* isolate() const
     {
         if (!m_isolate)
@@ skipping 60 matching lines @@
     bool isEmpty() const
     {
         return !m_value.get() || m_value->isEmpty();
     }
 
     void clear()
     {
         m_value = nullptr;
     }
 
-    v8::Handle<v8::Value> v8Value() const
-    {
-        return m_value.get() ? m_value->newLocal(isolate()) : v8::Handle<v8::Value>();
-    }
+    v8::Handle<v8::Value> v8Value() 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 WebCore
 
 #endif // ScriptValue_h