Quantize each vertex only once.

[treeform]

master:
svg render ........................ 15.088 ms     15.806 ms    ±1.377   x310

+ single quantize:
svg render ........................ 14.702 ms     14.836 ms    ±0.196   x334

with quantize x
svg render ........................ 14.827 ms     16.466 ms    ±1.607   x297

without quantize x
svg render ........................ 14.567 ms     14.923 ms    ±0.596   x328   ```