Fix #1060 - deal with browsers not supporting String.prototype.endsWith()
Fix #1060 - deal with browsers not supporting String.prototype.endsWith()

mozilla/thimble.mozilla.org,mozilla/thimble.mozilla.org,mozilla/thimble.mozilla.org,humphd/thimble.mozilla.org,humphd/thimble.mozilla.org,humphd/thimble.mozilla.org,humphd/thimble.mozilla.org,mozilla/thimble.mozilla.org