rg3/youtube-dl — pull request #1830 by jaimeMF (2013-11-25 22:03:13+00:00)
Title: Use the 'extractor_key' field for the download archive file

It has the same value as the ie_key.

For most video only extractors the `extractor` and `extractor_key` have the same values, but it's not true for all, for example the extractor for 56.com. If a video from this site is included in a playlist, we would never skip it.