When the object-browser columns exceeded the panel width, the vertical
scrollbar travelled with the content: the row scroller was stretched to
the content min-width inside the horizontally scrolling table container,
so its scrollbar sat at the far-right edge of the (off-screen) content
and users had to scroll all the way right to reach it (#8885).
The list scroller now stays viewport-width and owns the horizontal
scrolling itself (content min-width moves to the virtual-scroller item
wrapper), and the header becomes a clipped wrapper whose scrollLeft is
kept in sync with the scroller on scroll, resize, and re-attach.
wxp
3affa544a9