The proper way to test the existence of a property.
Fix for 'theater' mode.
Having some issues with 'apply' in the sandbox.

See greasemonkey/greasemonkey#1949
Migrating to the new addon API.
Make the request counter "static".
Run the script at "document-end".

This reverts da7d910. Said commit actually causes
the opposite effect with the HTML5 player.
Necessary evil.