Test cases for properties 50 to 53. (All properties now have test cases.)
Test cases for properties 50 to 53. (All properties now have test cases.)

svn path=/trunk/libcss/; revision=6118

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