Fix History.{push,replace}State handling of null 'url' argument

Source/core/page/History.cpp

 /*
  * Copyright (C) 2007 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 114 matching lines @@
         return;
 
     if (!activeDocument->canNavigate(m_frame))
         return;
 
     m_frame->navigationScheduler()->scheduleHistoryNavigation(distance);
 }
 
 KURL History::urlForState(const String& urlString)
 {
-    KURL baseURL = m_frame->document()->baseURL();
+    Document* document = m_frame->document();
+
+    if (urlString.isNull())
+        return document->url();
     if (urlString.isEmpty())
-        return baseURL;
+        return document->baseURL();
 
-    return KURL(baseURL, urlString);
+    return KURL(document->baseURL(), urlString);
 }
 
 void History::stateObjectAdded(PassRefPtr<SerializedScriptValue> data, const String& /* title */, const String& urlString, SameDocumentNavigationSource sameDocumentNavigationSource, ExceptionState& es)
 {
     if (!m_frame || !m_frame->page())
         return;
 
     KURL fullURL = urlForState(urlString);
     if (!fullURL.isValid() || !m_frame->document()->securityOrigin()->canRequest(fullURL)) {
         // We can safely expose the URL to JavaScript, as a) no redirection takes place: JavaScript already had this URL, b) JavaScript can only access a same-origin History object.
         es.throwSecurityError("A history state object with URL '" + fullURL.elidedString() + "' cannot be created in a document with origin '" + m_frame->document()->securityOrigin()->toString() + "'.");
         return;
     }
     m_frame->loader()->updateForSameDocumentNavigation(fullURL, sameDocumentNavigationSource, data, FrameLoader::DoNotUpdateBackForwardList);
 }
 
 } // namespace WebCore