XMLHttpRequest#responseText should use a rope

Source/core/inspector/InspectorResourceAgent.cpp

Index: Source/core/inspector/InspectorResourceAgent.cpp
diff --git a/Source/core/inspector/InspectorResourceAgent.cpp b/Source/core/inspector/InspectorResourceAgent.cpp
index 7773f99c1f655612d31405cf8ae12a53ddafecbb..078387e13426d12728c0e8d376ec47c795f02696 100644
--- a/Source/core/inspector/InspectorResourceAgent.cpp
+++ b/Source/core/inspector/InspectorResourceAgent.cpp
@@ -422,12 +422,12 @@ void InspectorResourceAgent::didFailXHRLoading(ThreadableLoaderClient* client)
     m_pendingXHRReplayData.remove(client);
 }
 
-void InspectorResourceAgent::didFinishXHRLoading(ThreadableLoaderClient* client, unsigned long identifier, const String& sourceString, const String&, const String&, unsigned)
+void InspectorResourceAgent::didFinishXHRLoading(ThreadableLoaderClient* client, unsigned long identifier, ScriptString sourceString, const String&, const String&, unsigned)
 {
     // For Asynchronous XHRs, the inspector can grab the data directly off of the CachedResource. For sync XHRs, we need to
     // provide the data here, since no CachedResource was involved.
     if (m_loadingXHRSynchronously)
-        m_resourcesData->setResourceContent(IdentifiersFactory::requestId(identifier), sourceString);
+        m_resourcesData->setResourceContent(IdentifiersFactory::requestId(identifier), sourceString.toString());
     m_pendingXHRReplayData.remove(client);
 }