PlatformImpl calls StyleManager.addUserAgentStylesheet for each stylesheet the platform needs. Each time addUserAgentStylesheet is called, CSS is totally re-evaluated, which adds to startup overhead. For an embedded linux device with touch-screen, css could be re-evaluated six times!

I propose to add a setUserAgentStylesheets(String... urls) to StyleManager that will process the stylesheets in bulk and re-evaluate CSS only once at the end.