Usage of nsIXMLHttpRequest Interface

 The update check was completed.
 @param   request
          The nsIXMLHttpRequest handling the update check.
 @param   updates
          An array of nsIUpdate objects listing available updates.
 @param   updateCount
          The size of the |updates| array.

void onCheckComplete(in nsIXMLHttpRequest request, [array, size_is(updateCount)] in nsIUpdate updates, in unsigned long updateCount)

 An error occurred while loading the remote update service file.
 @param   request
          The nsIXMLHttpRequest handling the update check.
 @param   update
          A nsIUpdate object that contains details about the
          error in its |statusText| property.

void onError(in nsIXMLHttpRequest request, in nsIUpdate update)

 Called every time there is a progress notification loading the Update
 Service file.
 @param   request
          The nsIXMLHttpRequest handling the update check.
 @param   position
          The current byte downloaded
 @param   totalSize
          The total number of bytes that have to be downloaded

void onProgress(in nsIXMLHttpRequest request, in unsigned long position, in unsigned long totalSize)