Scores are being miscomputed

[mgaudet]

I think there's a bit of a bug in 0746a31

Before

The aggregate metric geomean seems to be the sum of the sub-subtest results. Eg, if I look at http://localhost:8081/?developerMode=true&suites=Perf-Dashboard&startAutomatically=true#details from a locally served copy on 0746a31's parent I get

Perf-Dashboard/Render 	8.02 	± 	1.03 (12.9%) 	ms
Perf-Dashboard/SelectingPoints 	12.78 	± 	0.35 (2.7%) 	ms
Perf-Dashboard/SelectingRange 	8.42 	± 	1.04 (12.3%) 	ms

and

Geomean 	29.22 	± 	2.08 (7.1%) 	ms

After 0746a31

I get

Perf-Dashboard/Render 	7.50 	± 	0.37 (4.9%) 	ms
Perf-Dashboard/SelectingPoints 	13.98 	± 	1.57 (11.2%) 	ms
Perf-Dashboard/SelectingRange 	7.91 	± 	0.10 (1.2%) 	ms

and

Geomean 	7.91 	± 	0.10 (1.2%) 	ms

Which is exactly the result of SelectingRange -- it seems to overwrite the total.