Brackets Box/Flex CSS Update

[puzzledShark]

Presently brackets is using an outdated version of flex, due to this the sidebar is not rendered properly within firefox.

Refer to: https://github.com/humphd/brackets/issues/180 for more information on this issue/fix explaination

[abose]

@KeniMorri it looks like you have not signed the BRACKETS CONTRIBUTOR LICENSE AND DISTRIBUTION AGREEMENT

[le717]

I'd recommend holding off on merging this until Linux gets CEF 2721 so nothing breaks on that platform (and I think I heard something about that possibly happening in 1.4?).

[peterflynn]

Earlier, flexbox caused us some very bad performance issues. We should check:

a) whether this PR causes any performance regressions
b) whether this PR causes any performance improvements (maybe newer syntax uses a newer, faster impl under the hood) -- and if so, is it safe to start using flexbox more widely in the Brackets UI after this?

[puzzledShark]

Updated because I forgot to include prefixes for safari
@abose my bad, I've signed it now

[abose]

Marking this for 1.4, will update if there is any performance issues as peter pointed out.

[abose]

I see that there is an overlap in hte project tree rendering.

[redmunds]

@abose I just ran into a similar problem on an internal project (so I can't post any links). The solution for my particular case was to specify the min-height as the flex-basis parameter instead of auto, which is what Brackets appears to be doing -- see the .flex-item() mixin.

[abose]

Thanks @redmunds .
Waiting for PR to be updated with the fix.