Have XHR.getResponseHeader() return null in initial ready states.

Source/core/xml/XMLHttpRequest.cpp

 /*
  *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
  *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
  *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
@@ skipping 1039 matching lines @@
         result.iterator->value = result.iterator->value + ", " + value;
 }
 
 String XMLHttpRequest::getRequestHeader(const AtomicString& name) const
 {
     return m_requestHeaders.get(name);
 }
 
 String XMLHttpRequest::getAllResponseHeaders(ExceptionState& es) const
 {
-    if (m_state < HEADERS_RECEIVED) {
-        es.throwDOMException(InvalidStateError, ExceptionMessages::failedToExecute("getAllResponseHeaders", "XMLHttpRequest", "the object's state must not be UNSENT or OPENED."));
+    if (m_state < HEADERS_RECEIVED || m_error)
         return "";
-    }
 
     StringBuilder stringBuilder;
 
     HTTPHeaderSet accessControlExposeHeaderSet;
     parseAccessControlExposeHeadersAllowList(m_response.httpHeaderField("Access-Control-Expose-Headers"), accessControlExposeHeaderSet);
     HTTPHeaderMap::const_iterator end = m_response.httpHeaderFields().end();
     for (HTTPHeaderMap::const_iterator it = m_response.httpHeaderFields().begin(); it!= end; ++it) {
         // Hide Set-Cookie header fields from the XMLHttpRequest client for these reasons:
         //     1) If the client did have access to the fields, then it could read HTTP-only
         //        cookies; those cookies are supposed to be hidden from scripts.
@@ skipping 12 matching lines @@
         stringBuilder.append(it->value);
         stringBuilder.append('\r');
         stringBuilder.append('\n');
     }
 
     return stringBuilder.toString();
 }
 
 String XMLHttpRequest::getResponseHeader(const AtomicString& name, ExceptionState& es) const
 {
-    if (m_state < HEADERS_RECEIVED) {
-        es.throwDOMException(InvalidStateError, ExceptionMessages::failedToExecute("getResponseHeader", "XMLHttpRequest", "the object's state must not be UNSENT or OPENED."));
+    if (m_state < HEADERS_RECEIVED || m_error)
         return String();
-    }
 
     // See comment in getAllResponseHeaders above.
     if (isSetCookieHeader(name) && !securityOrigin()->canLoadLocalResources()) {
         logConsoleError(executionContext(), "Refused to get unsafe header \"" + name + "\"");
         return String();
     }
 
     HTTPHeaderSet accessControlExposeHeaderSet;
     parseAccessControlExposeHeadersAllowList(m_response.httpHeaderField("Access-Control-Expose-Headers"), accessControlExposeHeaderSet);
 
@@ skipping 262 matching lines @@
 {
     return EventTargetNames::XMLHttpRequest;
 }
 
 ExecutionContext* XMLHttpRequest::executionContext() const
 {
     return ActiveDOMObject::executionContext();
 }
 
 } // namespace WebCore