Add support for AbortController/AbortSignal (#4757)

cli/js/web/abort_controller.ts

@@ -0,0 +1,23 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { AbortSignalImpl, signalAbort } from "./abort_signal.ts";
+
+export class AbortControllerImpl implements AbortController {
+  #signal = new AbortSignalImpl();
+
+  get signal(): AbortSignal {
+    return this.#signal;
+  }
+
+  abort(): void {
+    this.#signal[signalAbort]();
+  }
+
+  get [Symbol.toStringTag](): string {
+    return "AbortController";
+  }
+}
+
+Object.defineProperty(AbortControllerImpl, "name", {
+  value: "AbortController",
+  configurable: true,
+});