adds the scrollbar only if the bottom one is present, does not recompute the top scrollbar
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH |
adds the scrollbar only if the bottom one is present, and recompute the top scrollbar size each time the window is resized
resize the window to try!!!!
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH | IIIIIIIII | JJJJJJJJJ |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH | IIIIIIIII | JJJJJJJJJ |
| AAAAAAAAA | BBBBBBBBB | CCCCCCCCC | DDDDDDDDD | EEEEEEEEE | FFFFFFFFF | GGGGGGGGG | HHHHHHHHH | IIIIIIIII | JJJJJJJJJ |