I've thought about this more over the past months and I think what we should do is aim to make Sheriff-o-Matic have similar font sizes and such to our other devtools like Monorail and PolyGerrit. (Gmail I think is actually also a pretty good example of a clean but still dense UI). 

I think just by decreasing the sizes on everything we can make things feel a lot more dense without making things feel cluttered. Right now, even collapsing all alerts on the Chromium Perf waterfall for example leaves the sections huge, so this is probably a pain for sheriffs to scan/deal with.