When closing single or multiple tabs, session state has historically capped the number of closed tabs being tracked. The main motivation was to prevent session file sizes on disk from getting too large.
When we introduced tab groups to session state, we avoided those caps when the tab group itself is being closed/saved. Users think of tab groups as whole entities. We were successfully saving tab groups with any number of tabs.
I introduced a regression causing closed tab groups and saved-and-closed tab groups to have their tab lists in session state capped. This patch resolves the regression by bypassing the cap when a closing tab is being closed as part of a tab group closing as a whole. Single or multiple tabs that are closed directly by the user should still be capped even if those tabs were in a tab group.
Differential Revision: https://phabricator.services.mozilla.com/D241087
a4e5d1a634