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 looks at three things:
- if the type has a typedef `AllowOwnPtr', respect that
- if not, disallow construction if both of `ref()' and `unref()' are
present.
Note that in the second case, if a type only defines `ref()' or only
defines `unref()', an OwnPtr can be created, as a RefPtr of that type
would be ill-formed.
Also marks a `Performance' to explicitly allow OwnPtrs.
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. :^)
