…d less.

Gecko’s CSS parsing microbenchmarks before:

```
  43.437 ±  0.391 ms    Stylo.Servo_StyleSheet_FromUTF8Bytes_Bench
  29.244 ±  0.042 ms    Stylo.Gecko_nsCSSParser_ParseSheet_Bench
 281.884 ±  0.028 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_Bench
 426.242 ±  0.008 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_WithInitialSpace_Bench
```

After:

```
  29.779 ±  0.254 ms    Stylo.Servo_StyleSheet_FromUTF8Bytes_Bench
  28.841 ±  0.031 ms    Stylo.Gecko_nsCSSParser_ParseSheet_Bench
 296.240 ±  4.744 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_Bench
 293.855 ±  4.304 ms    Stylo.Servo_DeclarationBlock_SetPropertyById_WithInitialSpace_Bench
```