When there's non-zero latency, saving the Settings Tray causes the plain Toolbar to be visible first

Problem/Motivation

On local development environments, everything seems fine. But those don't have any network latency.

On slower computers, slower browsers (think lots of extensions), or slower webservers (think xdebug enabled), this may also be visible.

As latency increases (as well as JS execution speed decreases), the problem becomes more pronounced. See the attached screencast → , which demonstrates the absence of the problem at zero/very low latency, the presence of it at some latency, and the prominence at very high latency.

Proposed resolution

TBD

Remaining tasks

User interface changes

API changes

Data model changes