On ios, Space Giraffe runs very slowly

[BryceLTaylor]

Expected Behavior

The project Space Giraffe, https://llk.github.io/scratch-gui/develop/#247578672, should run at a reasonable speed on all devices/browsers

Actual Behavior

It runs very slowly on ios

Steps to Reproduce

Load the project shown above
click the green flag
Note: after the "cover" sprite fades the giraffe head takes a long time to fall to the bottom.

Operating System and Browser

Safari on ios

[BryceLTaylor]

This may be related to this issue: #1663

[kyleplo]

Can’t repro on iPad Pro Chrome

[thisandagain]

/cc @mzgoddard @kchadha