CSS Fragmentation Module Level 3

2016-03-09: May share the navigation issues with other CSS specs. ACTION-2019 Fred to review.
2017-02-09: Has gone to CR.
2017-02-15: Action above never returned. We need to get the CSS TF to hussle.
2018-12-04: Republished as CR. We still gotta follow up.
2018-12-12: Defer review until the navigation exploration returns results.