TinyPilot doesn't respect cursor choice in fullscreen (OS X + Brave Browser)

[mtlynch]

A user reported to me that TinyPilot is losing their cursor choice in fullscreen. In normal viewing, they can see a custom cursor, but it reverts back to the default cursor in fullscreen.

To repro

1. Open the TinyPilot web app in the Brave browser on OS X
2. Go to View > Cursor > Crosshair
3. Go to View > Full Screen

Expected

Cursor icon is crosshairs

Actual

Cursor icon is the default cursor

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Note: I've attempted to repro on Win10 under both Chrome and Firefox, but I'm unable to reproduce.