Removed extremely slow Array.prototype.slice from hot path

[mcollina]

As titled :).

Where I am using this I got a a 10-20% throughput improvement with this change.

I'll ping you when I have something more solid on where I am using this.

[coveralls]

Coverage increased (+0.08%) to 95.96% when pulling 821eb96 on mcollina:master into 20f1dc5 on yoshuawuyts:master.

[yoshuawuyts]

This is great!

[yoshuawuyts]

Released as v6.2.2 🎉 🎉 🎉 🎉

[a0viedo]

@mcollina not seeing this in arbitrary big arrays (40M items) in latest versions of V8 (issue). I'll benchmark it in a few other engines and see what the results are.

[mcollina]

@a0viedo the problem is the use of arguments, not slice(). Your examples consider big arrays, but arguments is not an array.

[a0viedo]

oh I see!