Selection micro optimisation.
Selection micro optimisation.

svn path=/trunk/libcss/; revision=13120

zhuyadong/libcss,prepare/netsurf_libcss,servo/libcss,servo/libcss,zhuyadong/libcss,servo/libcss,prepare/netsurf_libcss,prepare/netsurf_libcss,zhuyadong/libcss