perf(primordials): Check the need for SafeArrayIterator each time

[petamoriken]

Closes #6

[CLAassistant]

All committers have signed the CLA.

[bartlomieju]

@petamoriken is there a test we could add here?

[petamoriken]

@bartlomieju I have no idea what tests to add for primordials.

[bartlomieju]

Does this PR introduce a change in behavior?

[petamoriken]

If Array.prototype[Symbol.iterator] and %ArrayIteratorPrototype%.next are not polluted, new SafeArrayIterator(arr) just returns arr without wrapping anything.

I believe this will improve performance, but don't know how to check performance.

[bartlomieju]

If Array.prototype[Symbol.iterator] and %ArrayIteratorPrototype%.next are not polluted, new SafeArrayIterator(arr) just returns arr without wrapping anything.

I believe this will improve performance, but don't know how to check performance.

You could create a benchmark that uses one object with these props and one without an then see the difference between execution times for say 100_000 items in the iterator.

You can see exmaple benchmarks in core/benches/ops/sync.rs

[mmastrac]

@petamoriken Would you still like to land this?

[petamoriken]

@mmastrac I am still inclined to work on it myself, but I don't mind having someone else do the work.