What steps will reproduce the problem?
(1) Open DevTools on a page with OOPIF iframes (e.g. gmail.com)
(2) Select an element in one treeoutline E1, then select another element in another OOPIF treeoutline E2.
(3) Click on E1 to select it again

What is the expected result?
Styles sidebar pane/breadcrumbs/UMA should treat this as a selection change and update

What happens instead?
Styles sidebar pane does not update, which leads me to think it is broken.