Add raf based measurement

[rniwa]

This PR adds a new query string parameter requestAnimationFrame, which takes the value of either "timer" or "raf". "timer" is the existing and default measurement method. When it's "raf", we use two consecutive requestAnimationFrame first of which runs the sync step and second of which schedules a 0s timer to signify the end of async step.

[camillobruni]

nice!

[camillobruni]

Modulo function-names / bind comment. Looking good!
Thanks for pulling this apart :)

[camillobruni]

As on the other PR, maybe named-methods + bind makes this more readable?

[rniwa]

What do you mean by that? Could you show me an example?

[camillobruni]

Along these lines (implying moving the *time values onto the class):

   const invoker = new invokerClass(this.measureSync.bind(this), this.measureAsync.bind(this), this._report.bind(this));
    ...
  }
  measureSync(...) {
   ...
  }
  measureAsync(...) {
    ...
  }
  ...

Maybe easier: using named arrow functions would be an improvement:

   ...
   const syncStart = () => {...};
   const measureAsync = () => {...};
   const report = () => {...};
   const invoker = new invokerClass(measureSync, measureAsync, report);
   

[smaug----]

.bind() makes it harder to read ;)
But that latter case looks better to me.

[rniwa]

Done that.

[camillobruni]

Maybe await invoker.start();

[smaug----]

r+ for the actual benchmark-runner. (I'm less familiar with test tests/* code).
Perhaps assign the callbacks to variables and pass those as params, that might improve the readability a bit.