I searched around and allegedly, body:nth-of-type(1) is used in CSS to target only Safari and Google Chrome.
body:nth-of-type(1)
Lo and behold, Mozilla reads it properly to
Any of the -webkit selectors should work for just Chrome and Safari.
http://qooxdoo.org/documentation/general/webkit_css_styles
Hope this is what you're looking for. Here's the webkit website:
http://webkit.org/