Prefer `.cloned()` over `.map(|x| x.clone())`

[frewsxcv]

https://doc.rust-lang.org/nightly/std/iter/trait.Iterator.html#method.cloned

https://doc.rust-lang.org/nightly/core/option/enum.Option.html#method.cloned

[pierrechevalier83]

see servo/servo#7946

[pierrechevalier83]

I didn't get it right... I got confused with servo/servo#7906 as explained in my comment there... Please, ignore! (I'm well intentioned, I swear... just a bit stupid...)

[wartmanm]

I didn't even realize cloned() was a thing! I'd like to tackle this, if I'm not being too greedy with easy/medium issues.

[Manishearth]

Sounds good to me!

Feel free to take as many mediums as you want. Easies too, but leave a couple of those for others 😄

[sanxiyn]

This can be closed, being fixed by #427.