This is real CSS handwritten by real people. It's not compressed, it's just not in a fully-expanded style. If your parser is slow for reasonably formatted CSS, then your parser is slow. The best case can be as fast as you want, but real-world use is what matters.
For what it's worth, -O2 brings the compile time for github.css down to about 1.5s.
No it's not. Look at it: it's one-selector-per-line, which is a very common style for handwritten CSS. If it were compressed, it would have no line breaks.
For what it's worth, -O2 brings the compile time for github.css down to about 1.5s.