Note: must do T423289 first.

Unify WMFAppViewController and WMFAppViewController+Extensions methods. Refactor WMFAppViewController feature-specific logic into coordinators. We want each of the 6 root tab views (Explore, Places, Saved, Activity, Search, and Settings when Explore is turned off) to instantiate through their own coordinator class. There are also other feature-specific handling methods which should live in a coordinator (for example, the WMFWatchlistDelegate methods). Once complete, ensure no regressions occur with the launch sequence and deep linking.

Eng Notes

• Tab Coordinator, which holds onto array of root feature coordinators
• Ensure these coordinators are retained correctly, watch out for retain cycles.