Issue #1587 - Part 7: Rename FetchController to AbortController

Also renames FetchSignal to AbortSignal. Includes renaming the various
controlling prefs to enable.

dom/abort/AbortSignal.h

@@ -0,0 +1,79 @@
+/* -*- 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/DOMEventTargetHelper.h"
+
+namespace mozilla {
+namespace dom {
+
+class AbortController;
+class AbortSignal;
+
+class AbortSignal final : public DOMEventTargetHelper
+{
+public:
+  // This class must be implemented by objects who want to follow a AbortSignal.
+  class Follower
+  {
+  public:
+    virtual void Aborted() = 0;
+
+  protected:
+    virtual ~Follower();
+
+    void
+    Follow(AbortSignal* aSignal);
+
+    void
+    Unfollow();
+
+    RefPtr<AbortSignal> mFollowingSignal;
+  };
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(AbortSignal, DOMEventTargetHelper)
+
+  AbortSignal(AbortController* aController, bool aAborted);
+  explicit AbortSignal(bool aAborted);
+
+  JSObject*
+  WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override;
+
+  bool
+  Aborted() const;
+
+  void
+  Abort();
+
+  IMPL_EVENT_HANDLER(abort);
+
+  void
+  AddFollower(Follower* aFollower);
+
+  void
+  RemoveFollower(Follower* aFollower);
+
+  bool
+  CanAcceptFollower(Follower* aFollower) const;
+
+private:
+  ~AbortSignal() = default;
+
+  RefPtr<AbortController> mController;
+
+  // Raw pointers. Follower unregisters itself in the DTOR.
+  nsTArray<Follower*> mFollowers;
+
+  bool mAborted;
+};
+
+} // dom namespace
+} // mozilla namespace
+
+#endif // mozilla_dom_AbortSignal_h