We have two known PlatformObjects that need to implement some of the
behavior of LegacyPlatformObjects to date: Window, and HTMLFormElement.
To make this not require double (or virtual) inheritance of
PlatformObject, move the behavior of LegacyPlatformObject into
PlatformObject. The selection of LegacyPlatformObject behavior is done
with a new bitfield of feature flags instead of a dozen virtual
functions that return bool. This change simplifies every class involved
in the diff with the notable exception of Window, which now needs some
ugly const casts to implement named property access.
With this change, we now have ~1200 CellAllocators across both LibJS and
LibWeb in a normal WebContent instance.
This gives us a minimum heap size of 4.7 MiB in the scenario where we
only have one cell allocated per type. Of course, in practice there will
be many more of each type, so the effective overhead is quite a bit
smaller than that in practice.
I left a few types unconverted to this mechanism because I got tired of
doing this. :^)
Stop worrying about tiny OOMs. Work towards #20449.
While going through these, I also changed the function signature in many
places where returning ThrowCompletionOr<T> is no longer necessary.
With the GC heap conversion, the functionality of legacy platform
objects was broken. This is because the generated implementation of one
of them was used for all of them, removing functionality such as
deletion.
This re-adds all functionality, where questions such as "does the
object support indexed properties?" is instead answered by virtual
functions instead of by the IDL generator checking the presence of
certain keywords/attributes.
Note that as of this commit, there aren't any such throwers, and the
call site in Heap::allocate will drop exceptions on the floor. This
commit only serves to change the declaration of the overrides, make sure
they return an empty value, and to propagate OOM errors frm their base
initialize invocations.
