CSSVacuum for Chrome
More About CSSVacuum
Google is recommending critical CSS be placed above the fold (https://docs.google.com/presentation/d/1IRHyU7_crIiCjl0Gvue0WY3eY_eYvFQvSfwQouW9368/present#slide=id.p19), and this plugin helps with that.
CSSVacuum finds elements that are above the fold, matches against all CSS classes, and regenerates CSS based on what is relevant (for you to copy and paste into header, or just look at when creating your critical.css file).
It is a tool to aid with development, and does not yet product 100% production grade CSS. Please contribute at https://github.com/ndreckshage/CSSVacuum.