Mark Kennedy
d779734d7e
Restores the user's scroll position when clicking browser back button when on a pane or sub-pane. Same behavior for the left arrow button next to sub-pane titles, but only if the sub-pane wasn't loaded by navigating to it from the URL-bar. * Supports restoring scroll position when going back from any pane (including sub panes) * Intentionally excludes breadcrumb clicks, since those are implicitly forward-moving entries * Uses ScrollOffets class but also refactors it to accommodate custom scroll targets and new use case in about:preferences Differential Revision: https://phabricator.services.mozilla.com/D301302