nsIConverterOutputStream in Firefox 3.0

 Initialize this stream. Must be called before any other method on this
 interface, or you will crash. The output stream passed to this method
 must not be null, or you will crash.

 @param aOutStream
        The underlying output stream to which the converted strings will
        be written.
 @param aCharset
        The character set to use for encoding the characters. A null
        charset will be interpreted as UTF-8.
 @param aBufferSize
        How many bytes to buffer. A value of 0 means that no bytes will be
        buffered. Implementations not supporting buffering may ignore
        this parameter.
 @param aReplacementCharacter
        The replacement character to use when an unsupported character is found.
        The character must be encodable in the selected character
        encoding; otherwise, attempts to write an unsupported character
        will throw NS_ERROR_LOSS_OF_SIGNIFICANT_DATA.

        A value of 0x0000 will cause an exception to be thrown upon
        attempts to write unsupported characters.