This is fundametally broken. A microtask only finishes after all
javascript has finished running. The selectedness of a select element
is observable by javascript, so any changes which are made as a result
of children changing associated with a select element should be made
through the children update steps and friends.
It is not cheap to do this, so only do it once within this function.
There is definitely some caching that we can do here, but this will
require some smart invalidation to detect _relevant_ changes in
the children.
This change ensures that the correct default value of 0 is used and
that values greater than 2147483647 will fall back to the default value.
It also splits the display size concept into a separate method, as
this isn't supposed to be used when getting the IDL property.
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
The main motivation behind this is to remove JS specifics of the Realm
from the implementation of the Heap.
As a side effect of this change, this is a bit nicer to read than the
previous approach, and in my opinion, also makes it a little more clear
that this method is specific to a JavaScript Realm.
