supporting nested imports

[shahabl]

Nested @imports don't work in firefox. As pointed out here
https://github.com/shahabl/brackets-livedev2/blob/feature/css/protocol/remote/MoreRemoteFunctions.js#L91-93
one way is to parse the CSS files when you open each as a live document and modify the url. To do this looks like we'll need to add files similar to HTMLSimpleDOM (and HTMLInstrumentation) to parse and modify the CSS. @dangoor, @njx please let me know if you have any suggestions on implementing this, or suggestion for other ways of getting firefox not to cache the css files.

[dangoor]

Is it possible for our server to serve up headers such that Firefox doesn't cache the content?

[busykai]

I made a patch for that yesterday while looking into CSS reload/flickering. Sending HTTP/1.1 Cache-Control. I'll pass it to Shahab to see if it helps the nested imports.

[busykai]

actually, it does not help. there's a 5 sec max-age which is specified specifically to avoid flickering in chrome, we could do it specifically for imports though. we will have to change the mechanism for collecting related documents to return the parent information for imported stylesheets -- to be able to re-create the tree on the editor side and refresh the parent (it's an overhead, but it does refresh all the imported styles as well).

@sebaslv found a promising solution for flickering in general which would help @imports as a side-effect.