The underlying container had width of 0.75 rem, which was equal to 12px
at default ui_font_size. However, with larger values of ui_font_size the
scrollbar would drift towards the center of a project panel, as the
scrollbar itself has a fixed width of 12 pixels. This commit moves
towards using a fixed width of 12px for scrollbar container. The
alternative was to make the scrollbar scale with ui_font_size, but that
isn't what the Editor scrollbar does, so I decided against it.
Release Notes:
- Fixed position of scrollbar in project panel with non-default
`ui_font_size` values.
22900554d5