Profile and remove dead optimizations

[benjamingr]

Hey, a lot of the performance optimizations here assume things about V8 that are no longer true with TurboFan.

This issue is to track and remove those eventually.

[lpinca]

Yes, we need to revisit some micro optimizations once TF+I lands (8.2.0?).
For example we can use Object.create(null) directly now instead of

function Storage() {}
Storage.prototype = Object.create(null);

which is nice as it will remove some feature detection code reducing the library size.

If you want to help tracing and removing dead optimizations please do, it will be greatly appreciated :)