Before this patch, it would only make the column visible on the edge of the viewport,
so that we could only see the breakpoint marker, and/or only the first character after the pause location.
With this patch, if the paused location is visible, nothing happens.
But if the paused location is outside of the viewport, the paused location is centered horizontally.
Differential Revision: https://phabricator.services.mozilla.com/D241173
47c1ea38e9