From:  "Fitzgerald, Nick" <nfitzgerald@mozilla.com>
Date:  26 Mar 2013 07:27:33 Hong Kong Time
Newsgroup:  news.mozilla.org/mozilla.dev.js-sourcemap
Subject:  

Proposal: make the "file" attribute optional

NNTP-Posting-Host:  63.245.216.66

Generally, if you are consuming a source map, then you know which file 
it belongs to. How else did you get the source map?

Can anyone think of a reason why it shouldn't be optional?

Nick