In the interests of maintainability (and some easy startup perf improvements), we should clean up the music metadata parser. This means: cleaning up the code style, splitting it out into multiple (lazy-loaded) files, using Promises where possible, and probably a few other things as I think of them.

Still WIP, but I've already reduced metadata.js by almost 50% in size.

Comment on attachment 8512271 [details] Pull request Ok, I think this is done. Sorry for making another huge metadata patch, but this should be the last time I need to do any big rewrites, since everything's now safely nestled in separate files.

Comment on attachment 8512271 [details] Pull request This looks like a really solid patch to me. I really like that each metadata format can be independently lazy loaded. I've left a bunch of comments on github. Almost all are minor. I think I only found two real errors and I think you've already fixed those.

Comment on attachment 8512271 [details] Pull request Looks good to me. Nothing to add from David thorough reviewing.

Oops, I forgot to squash this before landing, so I kind of made a mess of things. Anyway, here's the squashed merge commit: https://github.com/mozilla-b2g/gaia/commit/ace8153b0db6fa89f006f22f76ce338a258203c7