Add an ASSERT about cross-world wrapper leakage into ScriptValue

Source/web/WebPluginContainerImpl.cpp

 /*
  * Copyright (C) 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 424 matching lines @@
     if (!frame)
         return WebString();
 
     const KURL& kurl = url;
     ASSERT(kurl.protocolIs("javascript"));
 
     String script = decodeURLEscapeSequences(
         kurl.string().substring(strlen("javascript:")));
 
     UserGestureIndicator gestureIndicator(popupsAllowed ? DefinitelyProcessingNewUserGesture : PossiblyProcessingUserGesture);
-    ScriptValue result = frame->script().executeScriptInMainWorldAndReturnValue(ScriptSourceCode(script));
+    v8::HandleScope handleScope(toIsolate(frame));
+    v8::Local<v8::Value> result = frame->script().executeScriptInMainWorldAndReturnValue(ScriptSourceCode(script));
 
     // Failure is reported as a null string.
-    String resultString;
-    result.toString(resultString);
-    return resultString;
+    if (result.IsEmpty() || !result->IsString())
+        return WebString();
+    return toCoreString(v8::Handle<v8::String>::Cast(result));
 }
 
 void WebPluginContainerImpl::loadFrameRequest(const WebURLRequest& request, const WebString& target, bool notifyNeeded, void* notifyData)
 {
     LocalFrame* frame = m_element->document().frame();
     if (!frame || !frame->loader().documentLoader())
         return;  // FIXME: send a notification in this case?
 
     if (notifyNeeded) {
         // FIXME: This is a bit of hack to allow us to observe completion of
@@ skipping 439 matching lines @@
 
     return clipRect;
 }
 
 bool WebPluginContainerImpl::pluginShouldPersist() const
 {
     return m_webPlugin->shouldPersist();
 }
 
 } // namespace blink