Fix a bug that scrollbar width and height don't change when activating
Light theme. For example, when theming is inactive, change scrollbar
width from the default 16 pixels to 32 pixels, then activate Light theme.
Then scrollbar width should be changed to the theme specified scrollbar width.
Signed-off-by: Zhiyi Zhang <zzhang@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>