Asynchronously load a channel, converting the data to UTF-16.
To use this interface, first call init() with a
nsIUnicharStreamLoaderObserver that will be notified when the data has been
loaded. Then call asyncOpen() on the channel with the nsIUnicharStreamLoader
as the listener. The context argument in the asyncOpen() call will be
passed to the onStreamComplete() callback.
Initializes the unichar stream loader
| aObserver | the observer to notify when a charset is needed and when the load is complete |
The channel attribute is only valid inside the onDetermineCharset
and onStreamComplete callbacks. Otherwise it will be null.
The charset that onDetermineCharset returned, if that’s been
called.