[flex_next] Poor application performance when using a large css file

We have been attempting to migrate our application from Flex 3 to Flex 4 and encountered some performance issues. We found that our fairly large style sheet was one among the reasons for bad application performance in Flex 4.

I have attached a standalone app with our CSS file. The app does not use any style in the CSS, but just by including it in the app, the performance numbers are highly impacted. With the style sheet included the (empty) screen takes about 2 seconds to render (trace statement outputs the timings) and when the style sheet references are removed it takes about 1 second to render. However we found that the including the (Flex 3) style sheet does not have any impact on performance in Flex 3.5 (takes less than a second).

When profiling the application we found that an inordinate amount of time is being spent in following calls in 4.5:
StyleProtoChain.initProtoChain
StyleProtoChain.getMatchingStyleDeclarations
StyleProtoChain.matchStyleDeclarations

I think the numbers get better when we reduce the number of universal selectors in the CSS.