Only allow embeds on media_domain.
Only allow embeds on media_domain.

This prevents leaking of modhashes etc. from logged-in embeds.

florenceyeun/reddit-plugin-liveupdate,sim642/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate,madbook/reddit-plugin-liveupdate,sim642/reddit-plugin-liveupdate,florenceyeun/reddit-plugin-liveupdate,florenceyeun/reddit-plugin-liveupdate,sim642/reddit-plugin-liveupdate