Specification: https://dom.spec.whatwg.org/#concept-event-dispatch
This also introduces shadow roots due to it being a requirement of
the event dispatcher.
However, it does not introduce the full shadow DOM, that can be
left for future work.
This changes some event dispatches which require certain attributes
to be initialised to a value.
This is the origin timestamp of the same monotonic clock used for the
performance.now() timestamp.
I got a little confused while implementing this, since the numbers are
very low. That's because it uses the CLOCK_MONOTONIC system clock,
which we start counting from 0 at boot. :^)
This patch introduces the HighResolutionTime namespace which is home to
the Performance object (exposed via window.performance)
performance.now() is currently the only function, and it returns the
number of milliseconds since the window object was constructed. :^)
