This removes some ambiguity about what the return value should be if
the index is out of range.
Previously, we would sometimes return a JS null, and other times a JS
undefined.
It will also let us fold together the checks for whether an index is a
supported property index, followed by getting the value just afterwards.
This was resulting in a whole lot of rebuilding whenever a new IDL
interface was added.
Instead, just directly include the prototype in every C++ file which
needs it. While we only really need a forward declaration in each cpp
file; including the full prototype header (which itself only includes
LibJS/Object.h, which is already transitively brought in by
PlatformObject) - it seems like a small price to pay compared to what
feels like a full rebuild of LibWeb whenever a new IDL file is added.
Given all of these includes are only needed for the ::initialize
method, there is probably a smart way of avoiding this problem
altogether. I've considered both using some macro trickery or generating
these functions somehow instead.
This collection has some pretty strange behaviour, particularly with the
IsHTMLDDA slot which is defined in the javascript spec specifically for
this object.
This commit implements pretty much all of this interface, besides from
the custom [[Call]].
There is also no caching over this collection. Since it is a live
collection over the entire document, the performance is never going to
be great, and I am not convinced any speedup for this legacy interface
is worth a massive cache.
