XMLHttpRequest#responseText should use a rope

Source/core/inspector/InspectorInstrumentation.idl

 /*
 * 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 273 matching lines @@
     [Resource]
     void documentThreadableLoaderStartedLoadingForClient(ScriptExecutionContext*, unsigned long identifier, ThreadableLoaderClient* client);
 
     [Resource]
     void willLoadXHR(ScriptExecutionContext*, ThreadableLoaderClient* client, const String& method, const KURL& url, bool async, PassRefPtr<FormData>, const HTTPHeaderMap& headers, bool includeCredentials);
 
     [Resource]
     void didFailXHRLoading(ScriptExecutionContext*, ThreadableLoaderClient* client);
 
     [Console, Resource]
-    void didFinishXHRLoading(ScriptExecutionContext*, ThreadableLoaderClient* client, unsigned long identifier, const String& sourceString, const String& url, const String& sendURL, unsigned sendLineNumber);
+    void didFinishXHRLoading(ScriptExecutionContext*, ThreadableLoaderClient* client, unsigned long identifier, ScriptString sourceString, const String& url, const String& sendURL, unsigned sendLineNumber);
 
     [Resource]
     void didReceiveXHRResponse(ScriptExecutionContext*, unsigned long identifier);
 
     [Resource]
     void willLoadXHRSynchronously(ScriptExecutionContext*);
 
     [Resource]
     void didLoadXHRSynchronously(ScriptExecutionContext*);
 
@@ skipping 176 matching lines @@
 
     [Page, Inline=FastReturn]
     GeolocationPosition* overrideGeolocationPosition(Page* page, [DefaultReturn] GeolocationPosition* position);
 
     [Page, Inline=FastReturn]
     DeviceOrientationData* overrideDeviceOrientation(Page* page, [DefaultReturn] DeviceOrientationData* deviceOrientation);
 
     [Profiler]
     String getCurrentUserInitiatedProfileName(Page* page, bool incrementProfileNumber);
 }