We need to prevent these mutation observers from being garbage
collected, and since they are only part of SimilarOriginWindowAgent and
themselves as part of the intrusive list, nobody is visiting them.
Make the list of pending mutation observers a GC::RootVector so we keep
them alive until they have been processed in the microtask.
Restores 1400+ WPT subtest passes in `dom/nodes/Element-classlist.html`.
In the current spec, MutationObservers are explicitly added to the
pending mutation observers list, and they are removed when that list is
cleared in the "notify mutation observers" microtask.
This solves some issues with slotchange events.
As noted, we delay actually emptying the list of pending mutation
observers until after we're finished with the "clone", because we can't
actually copy or move the intrusive list. As far as I am aware, this
should not affect behaviour because only one microtask can run at once.
Before this change, Agent held on to all of the live MutationObserver
objects via GC::Root. This prevented them from ever getting
garbage-collected.
Instead of roots, we now use a simple IntrusiveList and remove them
from it in the finalizer for MutationObserver.
This fixes a massive GC leak on Speedometer.
We do not fire `beforeinput` events since other browsers do not seem to
do so either.
The spec asks us to check whether a command's action modified the DOM
tree. This means adding or removing nodes and attributes, or changing
character data anywhere in the tree. We have
`Document::dom_tree_version()` for node updates, but for character data
a new version number is introduced that allows us to easily keep track
of any text changes in the entire tree.
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
