We aren't getting enough out of this code to justify the complexity, and it's now broken on Julia master. So deleting for now. I've left the API in place, doing something roughly equivalent, so that it should not break any remaining uses in the rest of the Juno stack.
Nice, thanks for taking a look at this :) Didn't get around to it yet. I guess we should draft a Media.jl release with this change and then a Juno release that actually removes the @dynamic uses.
We aren't getting enough out of this code to justify the complexity, and it's now broken on Julia master. So deleting for now. I've left the API in place, doing something roughly equivalent, so that it should not break any remaining uses in the rest of the Juno stack.