mozilla/pdf.js — pull request #3459 by Rob--W (2013-07-10 21:36:33+00:00)
Title: Always declare window.URL even if undefined

Otherwise it breaks feature detection in https://github.com/mozilla/pdf.js/blob/e583070deb73113f13e7a5244138582b7a86140a/web/viewer.js#L1011
"ReferenceError: Can't find variable: URL" in Safari 5.1