15 files changed, 918 insertions, 0 deletions

diff --git a/dom/abort/AbortController.cpp b/dom/abort/AbortController.cpp
new file mode 100644
index 0000000000..9bd8202559
--- /dev/null
+++ b/dom/abort/AbortController.cpp
@@ -0,0 +1,80 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "AbortController.h"
+#include "AbortSignal.h"
+#include "js/Value.h"
+#include "mozilla/dom/AbortControllerBinding.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/HoldDropJSObjects.h"
+
+namespace mozilla::dom {
+
+NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE_WITH_JS_MEMBERS(AbortController,
+                                                      (mGlobal, mSignal),
+                                                      (mReason))
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(AbortController)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(AbortController)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(AbortController)
+  NS_WRAPPERCACHE_INTERFACE_MAP_ENTRY
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+/* static */
+already_AddRefed<AbortController> AbortController::Constructor(
+    const GlobalObject& aGlobal, ErrorResult& aRv) {
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  if (!global) {
+    aRv.Throw(NS_ERROR_FAILURE);
+    return nullptr;
+  }
+
+  RefPtr<AbortController> abortController = new AbortController(global);
+  return abortController.forget();
+}
+
+AbortController::AbortController(nsIGlobalObject* aGlobal)
+    : mGlobal(aGlobal), mAborted(false), mReason(JS::UndefinedHandleValue) {
+  mozilla::HoldJSObjects(this);
+}
+
+JSObject* AbortController::WrapObject(JSContext* aCx,
+                                      JS::Handle<JSObject*> aGivenProto) {
+  return AbortController_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+nsIGlobalObject* AbortController::GetParentObject() const { return mGlobal; }
+
+AbortSignal* AbortController::Signal() {
+  if (!mSignal) {
+    JS::Rooted<JS::Value> reason(RootingCx(), mReason);
+    mSignal = new AbortSignal(mGlobal, mAborted, reason);
+  }
+
+  return mSignal;
+}
+
+void AbortController::Abort(JSContext* aCx, JS::Handle<JS::Value> aReason) {
+  if (mAborted) {
+    return;
+  }
+
+  mAborted = true;
+
+  if (mSignal) {
+    mSignal->SignalAbort(aReason);
+  } else {
+    mReason = aReason;
+  }
+}
+
+AbortController::~AbortController() { mozilla::DropJSObjects(this); }
+
+}  // namespace mozilla::dom
diff --git a/dom/abort/AbortController.h b/dom/abort/AbortController.h
new file mode 100644
index 0000000000..0af33453cf
--- /dev/null
+++ b/dom/abort/AbortController.h
@@ -0,0 +1,56 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_AbortController_h
+#define mozilla_dom_AbortController_h
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsWrapperCache.h"
+
+class nsIGlobalObject;
+
+namespace mozilla {
+class ErrorResult;
+
+namespace dom {
+
+class AbortSignal;
+
+class AbortController : public nsISupports, public nsWrapperCache {
+ public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(AbortController)
+
+  static already_AddRefed<AbortController> Constructor(
+      const GlobalObject& aGlobal, ErrorResult& aRv);
+
+  explicit AbortController(nsIGlobalObject* aGlobal);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  nsIGlobalObject* GetParentObject() const;
+
+  AbortSignal* Signal();
+
+  void Abort(JSContext* aCx, JS::Handle<JS::Value> aReason);
+
+ protected:
+  virtual ~AbortController();
+
+  nsCOMPtr<nsIGlobalObject> mGlobal;
+  RefPtr<AbortSignal> mSignal;
+
+  bool mAborted;
+  JS::Heap<JS::Value> mReason;
+};
+
+}  // namespace dom
+}  // namespace mozilla
+
+#endif  // mozilla_dom_AbortController_h
diff --git a/dom/abort/AbortFollower.h b/dom/abort/AbortFollower.h
new file mode 100644
index 0000000000..9599960390
--- /dev/null
+++ b/dom/abort/AbortFollower.h
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_AbortFollower_h
+#define mozilla_dom_AbortFollower_h
+
+#include "jsapi.h"
+#include "nsISupportsImpl.h"
+#include "nsTObserverArray.h"
+#include "mozilla/WeakPtr.h"
+
+namespace mozilla::dom {
+
+class AbortSignal;
+class AbortSignalImpl;
+
+// This class must be implemented by objects who want to follow an
+// AbortSignalImpl.
+class AbortFollower : public nsISupports {
+ public:
+  virtual void RunAbortAlgorithm() = 0;
+
+  // This adds strong reference to this follower on the signal, which means
+  // you'll need to call Unfollow() to prevent your object from living
+  // needlessly longer.
+  void Follow(AbortSignalImpl* aSignal);
+
+  // Explicitly call this to let garbage collection happen sooner when the
+  // follower finished its work and cannot be aborted anymore.
+  void Unfollow();
+
+  bool IsFollowing() const;
+
+  AbortSignalImpl* Signal() const { return mFollowingSignal; }
+
+ protected:
+  virtual ~AbortFollower();
+
+  friend class AbortSignalImpl;
+
+  WeakPtr<AbortSignalImpl> mFollowingSignal;
+};
+
+class AbortSignalImpl : public nsISupports, public SupportsWeakPtr {
+ public:
+  explicit AbortSignalImpl(bool aAborted, JS::Handle<JS::Value> aReason);
+
+  bool Aborted() const;
+
+  // Web IDL Layer
+  void GetReason(JSContext* aCx, JS::MutableHandle<JS::Value> aReason);
+  // Helper for other DOM code
+  JS::Value RawReason() const;
+
+  virtual void SignalAbort(JS::Handle<JS::Value> aReason);
+
+ protected:
+  // Subclasses of this class must call these Traverse and Unlink functions
+  // during corresponding cycle collection operations.
+  static void Traverse(AbortSignalImpl* aSignal,
+                       nsCycleCollectionTraversalCallback& cb);
+
+  static void Unlink(AbortSignalImpl* aSignal);
+
+  virtual ~AbortSignalImpl() { UnlinkFollowers(); }
+
+  JS::Heap<JS::Value> mReason;
+
+ private:
+  friend class AbortFollower;
+
+  void MaybeAssignAbortError(JSContext* aCx);
+
+  void UnlinkFollowers();
+
+  // Raw pointers.  |AbortFollower::Follow| adds to this array, and
+  // |AbortFollower::Unfollow| (also called by the destructor) will remove
+  // from this array.  Finally, calling |SignalAbort()| will (after running all
+  // abort algorithms) empty this and make all contained followers |Unfollow()|.
+  nsTObserverArray<RefPtr<AbortFollower>> mFollowers;
+
+  bool mAborted;
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_AbortFollower_h
diff --git a/dom/abort/AbortSignal.cpp b/dom/abort/AbortSignal.cpp
new file mode 100644
index 0000000000..01d0ac947f
--- /dev/null
+++ b/dom/abort/AbortSignal.cpp
@@ -0,0 +1,327 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "AbortSignal.h"
+
+#include "mozilla/dom/AbortSignalBinding.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/EventBinding.h"
+#include "mozilla/dom/TimeoutHandler.h"
+#include "mozilla/dom/TimeoutManager.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/RefPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsPIDOMWindow.h"
+
+namespace mozilla::dom {
+
+// AbortSignalImpl
+// ----------------------------------------------------------------------------
+
+AbortSignalImpl::AbortSignalImpl(bool aAborted, JS::Handle<JS::Value> aReason)
+    : mReason(aReason), mAborted(aAborted) {
+  MOZ_ASSERT_IF(!mReason.isUndefined(), mAborted);
+}
+
+bool AbortSignalImpl::Aborted() const { return mAborted; }
+
+void AbortSignalImpl::GetReason(JSContext* aCx,
+                                JS::MutableHandle<JS::Value> aReason) {
+  if (!mAborted) {
+    return;
+  }
+  MaybeAssignAbortError(aCx);
+  aReason.set(mReason);
+}
+
+JS::Value AbortSignalImpl::RawReason() const { return mReason.get(); }
+
+// https://dom.spec.whatwg.org/#abortsignal-signal-abort steps 1-4
+void AbortSignalImpl::SignalAbort(JS::Handle<JS::Value> aReason) {
+  // Step 1.
+  if (mAborted) {
+    return;
+  }
+
+  // Step 2.
+  mAborted = true;
+  mReason = aReason;
+
+  // Step 3.
+  // When there are multiple followers, the follower removal algorithm
+  // https://dom.spec.whatwg.org/#abortsignal-remove could be invoked in an
+  // earlier algorithm to remove a later algorithm, so |mFollowers| must be a
+  // |nsTObserverArray| to defend against mutation.
+  for (RefPtr<AbortFollower>& follower : mFollowers.ForwardRange()) {
+    MOZ_ASSERT(follower->mFollowingSignal == this);
+    follower->RunAbortAlgorithm();
+  }
+
+  // Step 4.
+  UnlinkFollowers();
+}
+
+void AbortSignalImpl::Traverse(AbortSignalImpl* aSignal,
+                               nsCycleCollectionTraversalCallback& cb) {
+  ImplCycleCollectionTraverse(cb, aSignal->mFollowers, "mFollowers", 0);
+}
+
+void AbortSignalImpl::Unlink(AbortSignalImpl* aSignal) {
+  aSignal->mReason.setUndefined();
+  aSignal->UnlinkFollowers();
+}
+
+void AbortSignalImpl::MaybeAssignAbortError(JSContext* aCx) {
+  MOZ_ASSERT(mAborted);
+  if (!mReason.isUndefined()) {
+    return;
+  }
+
+  JS::Rooted<JS::Value> exception(aCx);
+  RefPtr<DOMException> dom = DOMException::Create(NS_ERROR_DOM_ABORT_ERR);
+
+  if (NS_WARN_IF(!ToJSValue(aCx, dom, &exception))) {
+    return;
+  }
+
+  mReason.set(exception);
+}
+
+void AbortSignalImpl::UnlinkFollowers() {
+  // Manually unlink all followers before destructing the array, or otherwise
+  // the array will be accessed by Unfollow() while being destructed.
+  for (RefPtr<AbortFollower>& follower : mFollowers.ForwardRange()) {
+    follower->mFollowingSignal = nullptr;
+  }
+  mFollowers.Clear();
+}
+
+// AbortSignal
+// ----------------------------------------------------------------------------
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(AbortSignal)
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(AbortSignal,
+                                                  DOMEventTargetHelper)
+  AbortSignalImpl::Traverse(static_cast<AbortSignalImpl*>(tmp), cb);
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(AbortSignal,
+                                                DOMEventTargetHelper)
+  AbortSignalImpl::Unlink(static_cast<AbortSignalImpl*>(tmp));
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(AbortSignal)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN_INHERITED(AbortSignal,
+                                               DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mReason)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_ADDREF_INHERITED(AbortSignal, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(AbortSignal, DOMEventTargetHelper)
+
+AbortSignal::AbortSignal(nsIGlobalObject* aGlobalObject, bool aAborted,
+                         JS::Handle<JS::Value> aReason)
+    : DOMEventTargetHelper(aGlobalObject), AbortSignalImpl(aAborted, aReason) {
+  mozilla::HoldJSObjects(this);
+}
+
+JSObject* AbortSignal::WrapObject(JSContext* aCx,
+                                  JS::Handle<JSObject*> aGivenProto) {
+  return AbortSignal_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+already_AddRefed<AbortSignal> AbortSignal::Abort(
+    GlobalObject& aGlobal, JS::Handle<JS::Value> aReason) {
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+
+  RefPtr<AbortSignal> abortSignal = new AbortSignal(global, true, aReason);
+  return abortSignal.forget();
+}
+
+class AbortSignalTimeoutHandler final : public TimeoutHandler {
+ public:
+  AbortSignalTimeoutHandler(JSContext* aCx, AbortSignal* aSignal)
+      : TimeoutHandler(aCx), mSignal(aSignal) {}
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS(AbortSignalTimeoutHandler)
+
+  // https://dom.spec.whatwg.org/#dom-abortsignal-timeout
+  // Step 3
+  MOZ_CAN_RUN_SCRIPT bool Call(const char* /* unused */) override {
+    AutoJSAPI jsapi;
+    if (NS_WARN_IF(!jsapi.Init(mSignal->GetParentObject()))) {
+      // (false is only for setInterval, see
+      // nsGlobalWindowInner::RunTimeoutHandler)
+      return true;
+    }
+
+    // Step 1. Queue a global task on the timer task source given global to
+    // signal abort given signal and a new "TimeoutError" DOMException.
+    JS::Rooted<JS::Value> exception(jsapi.cx());
+    RefPtr<DOMException> dom = DOMException::Create(NS_ERROR_DOM_TIMEOUT_ERR);
+    if (NS_WARN_IF(!ToJSValue(jsapi.cx(), dom, &exception))) {
+      return true;
+    }
+
+    mSignal->SignalAbort(exception);
+    return true;
+  }
+
+ private:
+  ~AbortSignalTimeoutHandler() override = default;
+
+  RefPtr<AbortSignal> mSignal;
+};
+
+NS_IMPL_CYCLE_COLLECTION(AbortSignalTimeoutHandler, mSignal)
+NS_IMPL_CYCLE_COLLECTING_ADDREF(AbortSignalTimeoutHandler)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(AbortSignalTimeoutHandler)
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(AbortSignalTimeoutHandler)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+static void SetTimeoutForGlobal(GlobalObject& aGlobal, TimeoutHandler& aHandler,
+                                int32_t timeout, ErrorResult& aRv) {
+  if (NS_IsMainThread()) {
+    nsCOMPtr<nsPIDOMWindowInner> innerWindow =
+        do_QueryInterface(aGlobal.GetAsSupports());
+    if (!innerWindow) {
+      aRv.ThrowInvalidStateError("Could not find window.");
+      return;
+    }
+
+    int32_t handle;
+    nsresult rv = innerWindow->TimeoutManager().SetTimeout(
+        &aHandler, timeout, /* aIsInterval */ false,
+        Timeout::Reason::eAbortSignalTimeout, &handle);
+    if (NS_FAILED(rv)) {
+      aRv.Throw(rv);
+      return;
+    }
+  } else {
+    WorkerPrivate* workerPrivate =
+        GetWorkerPrivateFromContext(aGlobal.Context());
+    workerPrivate->SetTimeout(aGlobal.Context(), &aHandler, timeout,
+                              /* aIsInterval */ false,
+                              Timeout::Reason::eAbortSignalTimeout, aRv);
+    if (aRv.Failed()) {
+      return;
+    }
+  }
+}
+
+// https://dom.spec.whatwg.org/#dom-abortsignal-timeout
+already_AddRefed<AbortSignal> AbortSignal::Timeout(GlobalObject& aGlobal,
+                                                   uint64_t aMilliseconds,
+                                                   ErrorResult& aRv) {
+  // Step 2. Let global be signal’s relevant global object.
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+
+  // Step 1. Let signal be a new AbortSignal object.
+  RefPtr<AbortSignal> signal =
+      new AbortSignal(global, false, JS::UndefinedHandleValue);
+
+  // Step 3. Run steps after a timeout given global, "AbortSignal-timeout",
+  // milliseconds, and the following step: ...
+  RefPtr<TimeoutHandler> handler =
+      new AbortSignalTimeoutHandler(aGlobal.Context(), signal);
+
+  // Note: We only supports int32_t range intervals
+  int32_t timeout =
+      aMilliseconds > uint64_t(std::numeric_limits<int32_t>::max())
+          ? std::numeric_limits<int32_t>::max()
+          : static_cast<int32_t>(aMilliseconds);
+
+  SetTimeoutForGlobal(aGlobal, *handler, timeout, aRv);
+  if (aRv.Failed()) {
+    return nullptr;
+  }
+
+  // Step 4. Return signal.
+  return signal.forget();
+}
+
+// https://dom.spec.whatwg.org/#dom-abortsignal-throwifaborted
+void AbortSignal::ThrowIfAborted(JSContext* aCx, ErrorResult& aRv) {
+  aRv.MightThrowJSException();
+
+  if (Aborted()) {
+    JS::Rooted<JS::Value> reason(aCx);
+    GetReason(aCx, &reason);
+    aRv.ThrowJSException(aCx, reason);
+  }
+}
+
+// https://dom.spec.whatwg.org/#abortsignal-signal-abort
+void AbortSignal::SignalAbort(JS::Handle<JS::Value> aReason) {
+  // Step 1, in case "signal abort" algorithm is called directly
+  if (Aborted()) {
+    return;
+  }
+
+  // Steps 1-4.
+  AbortSignalImpl::SignalAbort(aReason);
+
+  // Step 5.
+  EventInit init;
+  init.mBubbles = false;
+  init.mCancelable = false;
+
+  RefPtr<Event> event = Event::Constructor(this, u"abort"_ns, init);
+  event->SetTrusted(true);
+
+  DispatchEvent(*event);
+}
+
+void AbortSignal::RunAbortAlgorithm() {
+  JS::Rooted<JS::Value> reason(RootingCx(), Signal()->RawReason());
+  SignalAbort(reason);
+}
+
+AbortSignal::~AbortSignal() { mozilla::DropJSObjects(this); }
+
+// AbortFollower
+// ----------------------------------------------------------------------------
+
+AbortFollower::~AbortFollower() { Unfollow(); }
+
+// https://dom.spec.whatwg.org/#abortsignal-add
+void AbortFollower::Follow(AbortSignalImpl* aSignal) {
+  // Step 1.
+  if (aSignal->mAborted) {
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(aSignal);
+
+  Unfollow();
+
+  // Step 2.
+  mFollowingSignal = aSignal;
+  MOZ_ASSERT(!aSignal->mFollowers.Contains(this));
+  aSignal->mFollowers.AppendElement(this);
+}
+
+// https://dom.spec.whatwg.org/#abortsignal-remove
+void AbortFollower::Unfollow() {
+  if (mFollowingSignal) {
+    // |Unfollow| is called by cycle-collection unlink code that runs in no
+    // guaranteed order.  So we can't, symmetric with |Follow| above, assert
+    // that |this| will be found in |mFollowingSignal->mFollowers|.
+    mFollowingSignal->mFollowers.RemoveElement(this);
+    mFollowingSignal = nullptr;
+  }
+}
+
+bool AbortFollower::IsFollowing() const { return !!mFollowingSignal; }
+
+}  // namespace mozilla::dom
diff --git a/dom/abort/AbortSignal.h b/dom/abort/AbortSignal.h
new file mode 100644
index 0000000000..45c0390477
--- /dev/null
+++ b/dom/abort/AbortSignal.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_dom_AbortSignal_h
+#define mozilla_dom_AbortSignal_h
+
+#include "mozilla/dom/AbortFollower.h"
+#include "mozilla/DOMEventTargetHelper.h"
+
+namespace mozilla::dom {
+
+// AbortSignal the spec concept includes the concept of a child signal
+// "following" a parent signal -- internally, adding abort steps to the parent
+// signal that will then signal abort on the child signal -- to propagate
+// signaling abort from one signal to another.  See
+// <https://dom.spec.whatwg.org/#abortsignal-follow>.
+//
+// This requires that AbortSignal also inherit from AbortFollower.
+//
+// This ability to follow isn't directly exposed in the DOM; as of this writing
+// it appears only to be used internally in the Fetch API.  It might be a good
+// idea to split AbortSignal into an implementation that can follow, and an
+// implementation that can't, to provide this complexity only when it's needed.
+class AbortSignal : public DOMEventTargetHelper,
+                    public AbortSignalImpl,
+                    public AbortFollower {
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_INHERITED(AbortSignal,
+                                                         DOMEventTargetHelper)
+
+  AbortSignal(nsIGlobalObject* aGlobalObject, bool aAborted,
+              JS::Handle<JS::Value> aReason);
+
+  JSObject* WrapObject(JSContext* aCx,
+                       JS::Handle<JSObject*> aGivenProto) override;
+
+  IMPL_EVENT_HANDLER(abort);
+
+  static already_AddRefed<AbortSignal> Abort(GlobalObject& aGlobal,
+                                             JS::Handle<JS::Value> aReason);
+
+  static already_AddRefed<AbortSignal> Timeout(GlobalObject& aGlobal,
+                                               uint64_t aMilliseconds,
+                                               ErrorResult& aRv);
+
+  void ThrowIfAborted(JSContext* aCx, ErrorResult& aRv);
+
+  // AbortSignalImpl
+  void SignalAbort(JS::Handle<JS::Value> aReason) override;
+
+  // AbortFollower
+  void RunAbortAlgorithm() override;
+
+  virtual bool IsTaskSignal() const { return false; }
+
+ protected:
+  ~AbortSignal();
+};
+
+}  // namespace mozilla::dom
+
+#endif  // mozilla_dom_AbortSignal_h
diff --git a/dom/abort/moz.build b/dom/abort/moz.build
new file mode 100644
index 0000000000..eb5b25584a
--- /dev/null
+++ b/dom/abort/moz.build
@@ -0,0 +1,25 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "DOM: Core & HTML")
+
+TEST_DIRS += ["tests"]
+
+EXPORTS.mozilla.dom += [
+    "AbortController.h",
+    "AbortFollower.h",
+    "AbortSignal.h",
+]
+
+UNIFIED_SOURCES += [
+    "AbortController.cpp",
+    "AbortSignal.cpp",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/dom/abort/tests/mochitest.ini b/dom/abort/tests/mochitest.ini
new file mode 100644
index 0000000000..2d708e8aa2
--- /dev/null
+++ b/dom/abort/tests/mochitest.ini
@@ -0,0 +1,10 @@
+[DEFAULT]
+support-files =
+  worker_abort_controller_fetch.js
+  slow.sjs
+  !/dom/events/test/event_leak_utils.js
+
+[test_abort_controller.html]
+[test_abort_controller_fetch.html]
+[test_event_listener_leaks.html]
+skip-if = (os == "win" && processor == "aarch64") #bug 1535784
diff --git a/dom/abort/tests/moz.build b/dom/abort/tests/moz.build
new file mode 100644
index 0000000000..af8d7033c8
--- /dev/null
+++ b/dom/abort/tests/moz.build
@@ -0,0 +1,9 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+MOCHITEST_MANIFESTS += ["mochitest.ini"]
+
+XPCSHELL_TESTS_MANIFESTS += ["unit/xpcshell.ini"]
diff --git a/dom/abort/tests/slow.sjs b/dom/abort/tests/slow.sjs
new file mode 100644
index 0000000000..33a9c76b81
--- /dev/null
+++ b/dom/abort/tests/slow.sjs
@@ -0,0 +1,13 @@
+function handleRequest(request, response) {
+  response.processAsync();
+
+  let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
+  timer.init(
+    function () {
+      response.write("Here the content. But slowly.");
+      response.finish();
+    },
+    1000,
+    Ci.nsITimer.TYPE_ONE_SHOT
+  );
+}
diff --git a/dom/abort/tests/test_abort_controller.html b/dom/abort/tests/test_abort_controller.html
new file mode 100644
index 0000000000..a7181711d5
--- /dev/null
+++ b/dom/abort/tests/test_abort_controller.html
@@ -0,0 +1,73 @@
+<!--
+  Any copyright is dedicated to the Public Domain.
+  http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test AbortController</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+
+function testWebIDL() {
+  ok("AbortController" in self, "We have a AbortController prototype");
+  ok("AbortSignal" in self, "We have a AbortSignal prototype");
+
+  var ac = new AbortController();
+  ok(!!ac, "AbortController can be created");
+  ok(ac instanceof AbortController, "AbortController is a AbortController");
+
+  ok(!!ac.signal, "AbortController has a signal");
+  ok(ac.signal instanceof AbortSignal, "abortSignal is a AbortSignal");
+  is(ac.signal.aborted, false, "By default AbortSignal.aborted is false");
+  next();
+}
+
+function testUpdateData() {
+  var ac = new AbortController();
+
+  is(ac.signal.aborted, false, "By default AbortSignal.aborted is false");
+
+  ac.abort();
+  is(ac.signal.aborted, true, "Signal is aborted");
+
+  next();
+}
+
+function testAbortEvent() {
+  var ac = new AbortController();
+  ac.signal.onabort = function(e) {
+    is(e.type, "abort", "Abort received");
+    next();
+  };
+  ac.abort();
+}
+
+var steps = [
+  // Simple stuff
+  testWebIDL,
+  testUpdateData,
+
+  // Event propagation
+  testAbortEvent,
+];
+
+function next() {
+  if (!steps.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var step = steps.shift();
+  step();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+
+</script>
+</body>
+</html>
diff --git a/dom/abort/tests/test_abort_controller_fetch.html b/dom/abort/tests/test_abort_controller_fetch.html
new file mode 100644
index 0000000000..2342ecda89
--- /dev/null
+++ b/dom/abort/tests/test_abort_controller_fetch.html
@@ -0,0 +1,80 @@
+<!--
+  Any copyright is dedicated to the Public Domain.
+  http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Test AbortController in Fetch API</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<script class="testbody" type="text/javascript">
+
+function testAbortedFetch() {
+  var ac = new AbortController();
+  ac.abort();
+
+  fetch("slow.sjs", { signal: ac.signal }).then(() => {
+    ok(false, "Fetch should not return a resolved promise");
+  }, e => {
+    is(e.name, "AbortError", "We have an abort error");
+  }).then(next);
+}
+
+function testFetchAndAbort() {
+  var ac = new AbortController();
+
+  var p = fetch("slow.sjs", { signal: ac.signal });
+  ac.abort();
+
+  p.then(() => {
+    ok(false, "Fetch should not return a resolved promise");
+  }, e => {
+    is(e.name, "AbortError", "We have an abort error");
+  }).then(next);
+}
+
+function testWorkerAbortedFetch() {
+  var w = new Worker("worker_abort_controller_fetch.js");
+  w.onmessage = function(e) {
+    ok(e.data, "Abort + Fetch works in workers");
+    next();
+  };
+  w.postMessage("testWorkerAbortedFetch");
+}
+
+function testWorkerFetchAndAbort() {
+  var w = new Worker("worker_abort_controller_fetch.js");
+  w.onmessage = function(e) {
+    ok(e.data, "Abort + Fetch works in workers");
+    next();
+  };
+  w.postMessage("testWorkerFetchAndAbort");
+}
+
+var steps = [
+  // fetch + signaling
+  testAbortedFetch,
+  testFetchAndAbort,
+  testWorkerAbortedFetch,
+  testWorkerFetchAndAbort,
+];
+
+function next() {
+  if (!steps.length) {
+    SimpleTest.finish();
+    return;
+  }
+
+  var step = steps.shift();
+  step();
+}
+
+SimpleTest.waitForExplicitFinish();
+next();
+
+</script>
+</body>
+</html>
diff --git a/dom/abort/tests/test_event_listener_leaks.html b/dom/abort/tests/test_event_listener_leaks.html
new file mode 100644
index 0000000000..f9684e2309
--- /dev/null
+++ b/dom/abort/tests/test_event_listener_leaks.html
@@ -0,0 +1,43 @@
+<!--
+  Any copyright is dedicated to the Public Domain.
+  http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<!DOCTYPE HTML>
+<html>
+<head>
+  <title>Bug 1450271 - Test AbortSignal event listener leak conditions</title>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="text/javascript" src="/tests/dom/events/test/event_leak_utils.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<script class="testbody" type="text/javascript">
+
+// Manipulate AbortSignal.  Its important here that we create a
+// listener callback from the DOM objects back to the frame's global
+// in order to exercise the leak condition.
+async function useAbortSignal(contentWindow) {
+  let controller = new contentWindow.AbortController();
+  let signal = controller.signal;
+  signal.onabort = _ => {
+    contentWindow.abortCount += 1;
+  };
+}
+
+async function runTest() {
+  try {
+    await checkForEventListenerLeaks("AbortSignal", useAbortSignal);
+  } catch (e) {
+    ok(false, e);
+  } finally {
+    SimpleTest.finish();
+  }
+}
+
+SimpleTest.waitForExplicitFinish();
+addEventListener("load", runTest, { once: true });
+</script>
+</pre>
+</body>
+</html>
diff --git a/dom/abort/tests/unit/test_abort.js b/dom/abort/tests/unit/test_abort.js
new file mode 100644
index 0000000000..c1586443cb
--- /dev/null
+++ b/dom/abort/tests/unit/test_abort.js
@@ -0,0 +1,8 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+function run_test() {
+  let ac = new AbortController();
+  Assert.ok(ac instanceof AbortController);
+  Assert.ok(ac.signal instanceof AbortSignal);
+}
diff --git a/dom/abort/tests/unit/xpcshell.ini b/dom/abort/tests/unit/xpcshell.ini
new file mode 100644
index 0000000000..219daa771a
--- /dev/null
+++ b/dom/abort/tests/unit/xpcshell.ini
@@ -0,0 +1,5 @@
+[DEFAULT]
+head =
+support-files =
+
+[test_abort.js]
diff --git a/dom/abort/tests/worker_abort_controller_fetch.js b/dom/abort/tests/worker_abort_controller_fetch.js
new file mode 100644
index 0000000000..571d9ffc7e
--- /dev/null
+++ b/dom/abort/tests/worker_abort_controller_fetch.js
@@ -0,0 +1,33 @@
+function testWorkerAbortedFetch() {
+  var ac = new AbortController();
+  ac.abort();
+
+  fetch("slow.sjs", { signal: ac.signal }).then(
+    () => {
+      postMessage(false);
+    },
+    e => {
+      postMessage(e.name == "AbortError");
+    }
+  );
+}
+
+function testWorkerFetchAndAbort() {
+  var ac = new AbortController();
+
+  var p = fetch("slow.sjs", { signal: ac.signal });
+  ac.abort();
+
+  p.then(
+    () => {
+      postMessage(false);
+    },
+    e => {
+      postMessage(e.name == "AbortError");
+    }
+  );
+}
+
+self.onmessage = function (e) {
+  self[e.data]();
+};