Simplifying logic to toggle debug bird's eye mode during flythrough
Simplifying logic to toggle debug bird's eye mode during flythrough

It's simpler to directly create the `DebugAnimationController` instance
than to set a flag indicating it should be created later. There's no
reason why it can't be created immediately, and this also simplifies
`tick()` and makes it's structure more clear.

jstrait/webgl-city,jstrait/webgl-city