change the existing implementation from using
```
string.split(/\s+/);
```
to a char scan which performers the same thing.
The reason why `split(/\s+/)` is slow is that:
- `/\s+/` allocates new `RegExp` every time this code executes.
- `RegExp` scans are a lot more expensive because they are more powerful.
PR Close#33326
Misko Hevery