Instant::now does not work in Web Workers

[knpwrs]

This library was working excellently until I tried to port some code I wrote to run in a web worker rather than in the main process. window does not exist in web workers, so web_sys::window() fails. That said, self.performance() is a thing in web workers so I think this module should be able to be updated to work in all browser environments.

This is the behavior I'm seeing using this module in a web worker: rustwasm/wasm-bindgen#1046

EDIT: To be specific, Instant::now() is not working inside of web workers because web_sys::window() does not work there. I'm hoping there's still a way to somehow access self.performance.now() inside a web worker using this module.

[knpwrs]

The gloo project had to fix a similar issue: rustwasm/gloo#56

I'm not sure how much work it would be to implement a similar solution here. It seems as though web_sys only directly supports performance off of web_sys::window() and not web_sys::global().

[knpwrs]

There is a similar issue opened for the web-sys crate: rustwasm/wasm-bindgen#1752