nsIDownload Interface

 Optional. If set, it will contain the target's relevant MIME information.
 This includes it's MIME Type, helper app, and whether that helper should be
 executed.

readonly attribute nsIMIMEInfo MIMEInfo

 The amount of kbytes downloaded so far.

readonly attribute PRUint64 amountTransferred

 Object that can be used to cancel the download.
 Will be null after the download is finished.

readonly attribute nsICancelable cancelable

 The user-readable description of the transfer.

readonly attribute wstring displayName

 The percentage of transfer completed.
 If the file size is unknown it'll be -1 here.

readonly attribute PRInt32 percentComplete

 The size of file in kbytes.
 Unknown size is represented by 0.

readonly attribute PRUint64 size

 The source of the transfer.

readonly attribute nsIURI source

 The time a transfer was started.

readonly attribute long long startTime

 The target of the transfer.

readonly attribute nsIURI target

 The target of a download is always a file on the local file system.

readonly attribute nsILocalFile targetFile