Some time ago in  Issue 456507  it was reported that some Three.js stress tests dropped in performance. It seems they've since been fixed very recently. We should add these to the tough_webgl_cases assuming they're stable and robust enough on the perf bots.

Specifically, let's add:

http://threejs.org/examples/webgl_performance.html
http://threejs.org/examples/webgl_performance_static.html
http://threejs.org/examples/webgl_sandbox.html

to src/tools/perf/page_sets/tough_webgl_cases.py , and produce any WPRs necessary. Then we can see whether the numbers they generate will be stable enough over time.

Brandon, may I assign this to you since you're the owner of these tests?