These allow accessing embeds, forms, images and objects with a given
name attribute, and any element with a given id attribute, as top level
properties on the global object.
It also allows accessing NavigableContainers by target name as top level
properties on the global object.
The current implementation feels very expensive. It's likely that
these values will need smarter caching in the future.
And implement WindowProperties, the "named properties object" for Window
according to the spec.
This involves moving an AO out of LegacyPlatformObject and into a common
place that the WindowProperties class can access.
This doesn't implement the AOs on Window that actually name lookup for
the unenumerable named properties on the window yet, just the
scaffolding.
We skip serializing any of the internal state of the Regex<ECMA262>
object, because that state is all computable from the input pattern
and flags. If it turns out that this is really, really slow, we can add
some optimizations to serialize more of the regex parse result.
The invariants for these property getters are supposed to be checked by
the has_entries_and_events_disabled AO, but we don't have all the
plumbing hooked up between Navigables and Navigation yet.
Add a test to make sure that these methods don't assert when calling
them on a fresh page.
