Replace the blocking spin_processing_tasks_with_source_until calls
in apply_the_history_step_after_unload_check() with an event-driven
ApplyHistoryStepState GC cell that tracks 5 phases, following the
same pattern used by CheckUnloadingCanceledState.
Key changes:
- Introduce ApplyHistoryStepState with phases:
WaitingForDocumentPopulation, ProcessingContinuations,
WaitingForChangeJobCompletion, WaitingForNonChangingJobs and Completed
- Add on_complete callbacks to apply_the_push_or_replace_history_step,
finalize_a_same_document_navigation,
finalize_a_cross_document_navigation, and
update_for_navigable_creation_or_destruction
- Remove spin_until from Document::open()
- Use null-document tasks for non-changing navigable updates and
document unload/destroy to avoid stuck tasks when documents become
non-fully-active
- Defer completely_finish_loading when document has no navigable yet,
and re-trigger post-load steps in activate_history_entry for documents
that completed loading before activation
Co-Authored-By: Shannon Booth <shannon@serenityos.org>
This begins implementation on form-associated custom elements.
This fixes a few WPT tests which I'm importing.
Co-authored-by: Sam Atkins <sam@ladybird.org>
