[css-flexbox] bikeshed improvements

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extra : rebase_source : f01b65220a5ae6b43eb42239bd955a17d191d56c
[css-fonts] Initial conversion pass done. Spec building successfully, but so many errors, just so many.

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extra : rebase_source : 799949a64c388f94df725feacd558e8f26c0cbba