nsIMultiPartChannel Interface

 readonly attribute to access the underlying channel

readonly attribute nsIChannel baseChannel

 Access to the Content-Disposition header field of this part of
 a multipart message.  This allows getting the preferred
 handling method, preferred filename, etc.  See RFC 2183.

attribute ACString contentDisposition

 Set to true when onStopRequest is received from the base channel.
 The listener can check this from its onStopRequest to determine
 whether more data can be expected.

readonly attribute boolean isLastPart

 Attribute guaranteed to be different for different parts of
 the same multipart document.

readonly attribute PRUint32 partID