UndoReducer

Element	Missed Instructions	Cov.	Missed Branches	Cov.	Missed	Cxty	Missed	Lines	Missed	Methods
Total	71 of 226	68%	3 of 10	70%	3	6	5	22	0	1
reduce(BrowserState, UndoAction)		68%		70%	3	6	5	22	0	1