What

Installs the DOM Standard's abort primitives as globals in every isolate (main and workers), modeled on Node's internal/abort_controller.js:

• AbortController — controller.signal (stable identity) and controller.abort(reason?).
• AbortSignal extending the runtime's EventTarget, with aborted, reason, throwIfAborted(), the abort event, and onabort with HTML event-handler semantics. new AbortSignal() throws TypeError: Illegal constructor.
• Statics: AbortSignal.abort(reason?), AbortSignal.timeout(delay) (Node's delay validation), and AbortSignal.any(signals) (composite flattening, first-aborted-reason-wins, spec-ordered state flips before events fire).
• WebIDL-shaped interfaces: enumerable members, Symbol.toStringTag, brand-checked accessors (via private fields).

How

The builtin (NativeScript/runtime/js/abort-signal.js) runs from Events::Init immediately after the Event/EventTarget builtin it is layered on.

This PR also introduces a sixth fixed wrapper parameter, internals: one plain per-isolate object (a Caches::StateFor slot) handed identically to every builtin and reachable from nowhere app code can see — the private channel for cross-builtin capabilities. Both previously ad-hoc channels now ride it: the kListenerChanged hook key (events → abort-signal) and setListenerErrorReporter (error-events → events), replacing the _installListenerErrorReporter one-shot that transiently sat on the app-reachable global target. Documented in the js README as an interim mechanism, with the intended end-state being a Node-style private internal-module tier (require("internal/…") for builtins only). RangeError, NumberIsInteger, WeakRef, and FinalizationRegistry are added to primordials (and the eslint restriction lists).

GC contract (Node-equivalent, documented in docs/abort-signal.md)

Internal references never keep an unobservable signal alive and never drop an observable abort:

• timeout() timers close over a WeakRef; a FinalizationRegistry cancels the pending native timer if the signal is collected first.
• any() links are WeakRefs in both directions with prune registries, so per-request composites never accumulate on a long-lived source, and a composite whose sources all died stops being retained.
• A gcPersistentSignals set strong-holds exactly the signals whose abort someone can still observe: live timeout signals and non-empty composites while they have abort listeners, plus timeout sources a composite follows until their timer fires. The listener accounting comes from a new symbol-keyed listener-mutation hook in events.js (called from add, remove, and the once-splice during dispatch), published on the builtin-only internals channel — so it cannot be bypassed via a captured EventTarget.prototype.addEventListener.

Deviation from Node

No DOMException in this runtime: default reasons are Error instances with name patched to "AbortError" / "TimeoutError", the same stand-in performance.js and structured-clone.js use.

Tests

• 20 behavioral specs: illegal constructor, state-flips-before-event ordering, reason identity (including null), throwing listeners not stopping dispatch, once listeners, onabort set/replace/clear, delay validation, any() flattening/dedup/no-double-fire, arbitrary iterables, toStringTag, brand checks.
• 8 GC specs driven by __collect(): a finalization-registry substrate canary, collectability of unobserved timeout signals and composites, survival (and delivery) for listened ones, a composite keeping a dropped timeout source alive until it fires, release of a listened composite once its last source dies, and release on last-listener removal.

Full iOS suite passes with 0 failures.