Couldn't create nsIXMLHttpRequest instance! Source Code

In Firfox's Source TestNativeXMLHttpRequest.cpp 
xhr  Is Null
 1
  nsCOMPtr<nsIXMLHttpRequest> xhr =
    do_CreateInstance(NS_XMLHTTPREQUEST_CONTRACTID, &rv);
  TEST_ENSURE_SUCCESS(rv, "Couldn't create nsIXMLHttpRequest instance!");
  NS_NAMED_LITERAL_CSTRING(getString, "GET");
  NS_NAMED_LITERAL_CSTRING(testURL, TEST_URL);
  const nsAString& empty = EmptyString();
  
  printf("*** About to see an expected warning about mPrincipal:\n");
  rv = xhr->OpenRequest(getString, testURL, PR_FALSE, empty, empty);
  printf("*** End of expected warning output.\n");
  TEST_ENSURE_FAILED(rv, "OpenRequest should have failed!");

2 Other Way
  nsCOMPtr<nsIXMLHttpRequest> request = do_GetService(NS_XMLHTTPREQUEST_CONTRACTID, &rv); 
  The request  is Null also

AnyBody Know how to Create nsIXMLHttpRequest instance?
My SDK IS Gecko_SDK 1.9.2

Thanks.


2010-09-13 



tanbo19820704