4836: Trigger Workbench infinite scroll load on tab show.

4836: Trigger Workbench infinite scroll load on tab show.

If an infinite scroller is in the first tab of a show page, but the
user is going to a different tab, we'll queue up the first event
to load data for the container, but when it fires the container won't
be visible so it will decline to load anything.  Then you can only get
data to load if you resize the window.

Fire a scroll event when a new tab is shown, to spur the infinite
scroller to load data as appropriate.