performance sign-off

[pixelzoom]

This is an item from the Master Checklist, to be completed by the Lead Designer.

[pixelzoom]

@arouinfar This is ready for your review. You can use master or 1.0.0-dev.36.

The worst-case scenario is shown below: the Energy screen with 2000 particles, all accordion boxes expanded, all 4 "species histogram" checkboxes checked (histograms are updated only when visible), and the stopwatch running.

Please identify any platforms where we might need to squeeze out more performance.

[arouinfar]

@pixelzoom performance is looking pretty smooth, even in the worst-case scenario described in #98 (comment).

According to @KatieWoe we no longer support iOS 9 or iOS 10, so I tested dev.36 on these devices:

• Chadwick, Chromebook running latest Chrome (74.0.3729.159)
• Pauling, iPad Air 2, iOS 11.3
• Leibniz, iPair Air 2, iOS 12

The iPads had a pretty low frame rate (~15 FPS) in the worst-case scenario, but the particle animation still looked reasonable and UI elements all remained responsive with no noticeable lag.