Linux Mac OSX Windows 
 nsIUnicharStreamListener is very similar to nsIStreamListener with
 the difference being that this interface gives notifications about
 data being available after the raw data has been converted to
 UTF-16.

 nsIUnicharStreamListener

 @status FROZEN
[scriptable, uuid(4a7e9b62-fef8-400d-9865-d6820f630b4c)]
interface nsIUnicharStreamListener : nsIRequestObserver

Methods

 Called when the next chunk of data (corresponding to the
 request) is available.

 @param aRequest request corresponding to the source of the data
 @param aContext user defined context
 @param aData the data chunk

 An exception thrown from onUnicharDataAvailable has the
 side-effect of causing the request to be canceled.
void onUnicharDataAvailable(in nsIRequest aRequest, in nsISupports aContext, in AString aData)