[css3-flexbox] nit on "contents" language in anonymous flex items section

One nit in the current flexbox ED:

 # 4. Flex Items
 # [...]
 #   4. An anonymous block [...]. However, if the contents of the
 # anonymous block would contain solely an anonymous inline
 # containing only whitespace, the box is not generated, as if it
 # had ‘display:none’.

"if the contents...would contain" is a bit odd there.

I think it wants s/if the contents of/if/

Thanks,
~Daniel