fix: Polyfill missing AbortController on Tizen (shaka-project#4707)

We started using AbortController in HlsParser in 777c27e, but that
change was made while the Tizen TV in our lab was offline. This restores
functionality to Tizen.

This polyfill uses getters, a feature of ES6 that the compiler won't
transpile into ES3, so this also changes the output language to ES5.
This should not be an issue, since ES5 has been well supported in all
browsers since IE10.

build/build.py

@@ -54,7 +54,7 @@
 shaka_version = shakaBuildHelpers.calculate_version()
 
 common_closure_opts = [
-    '--language_out', 'ECMASCRIPT3',
+    '--language_out', 'ECMASCRIPT5',
 
     '--jscomp_error=*',
 

build/conformance.textproto

@@ -269,6 +269,7 @@ requirement: {
   whitelist_regexp: "demo/"
   whitelist_regexp: "test/"
   whitelist_regexp: "lib/util/delayed_tick.js"
+  whitelist_regexp: "lib/polyfill/abort_controller.js"
 }
 requirement: {
   type: BANNED_NAME

build/types/polyfill

@@ -1,6 +1,7 @@
 # Polyfills used to emulate missing browsers features.
 
 +../../node_modules/eme-encryption-scheme-polyfill/index.js
++../../lib/polyfill/abort_controller.js
 +../../lib/polyfill/aria.js
 +../../lib/polyfill/encryption_scheme.js
 +../../lib/polyfill/fullscreen.js

lib/polyfill/abort_controller.js

@@ -0,0 +1,143 @@
+/*! @license
+ * Shaka Player
+ * Copyright 2016 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+goog.provide('shaka.polyfill.AbortController');
+
+goog.require('shaka.polyfill');
+goog.require('shaka.util.FakeEvent');
+goog.require('shaka.util.FakeEventTarget');
+
+/**
+ * @summary A polyfill for systems that do not implement AbortController.
+ * This is used both with the fetch API for HTTP requests and inside the HLS
+ * parser.
+ * @export
+ * @extends AbortController
+ */
+shaka.polyfill.AbortController = class {
+  /**
+   * Install the polyfill if needed.
+   * @export
+   */
+  static install() {
+    if (window.AbortController) {
+      // Not needed.
+      return;
+    }
+
+    window.AbortController = shaka.polyfill.AbortController;
+    window.AbortSignal = shaka.polyfill.AbortController.AbortSignal;
+  }
+
+  /** */
+  constructor() {
+    /** @private {!shaka.polyfill.AbortController.AbortSignal} */
+    this.signal_ = new shaka.polyfill.AbortController.AbortSignal();
+  }
+
+  /**
+   * @override
+   * @suppress {const|duplicate} Since the original is defined as "const", we
+   *   need this suppression to override it.
+   */
+  get signal() {
+    return this.signal_;
+  }
+
+  /**
+   * @param {*=} reason
+   * @override
+   */
+  abort(reason) {
+    this.signal_.doAbort_(reason);
+  }
+};
+
+/**
+ * @summary A polyfill for AbortSignal, part of the AbortController API.
+ * @implements {AbortSignal}
+ */
+shaka.polyfill.AbortController.AbortSignal =
+class extends shaka.util.FakeEventTarget {
+  /** */
+  constructor() {
+    super();
+
+    /** @private {boolean} */
+    this.aborted_ = false;
+
+    /** @private {*} */
+    this.reason_ = undefined;
+
+    /** @type {?function(!Event)} */
+    this.onabort = null;
+  }
+
+  /** @override */
+  get aborted() {
+    return this.aborted_;
+  }
+
+  /** @return {*} */
+  get reason() {
+    return this.reason_;
+  }
+
+  /**
+   * @param {*} reason
+   * @private
+   */
+  doAbort_(reason) {
+    if (this.aborted_) {
+      return;
+    }
+
+    this.aborted_ = true;
+    this.reason_ = reason;
+    if (this.reason_ === undefined) {
+      // This is equivalent to a native implementation.
+      this.reason_ = new DOMException(
+          'signal is aborted without reason', 'AbortError');
+    }
+
+    // According to MDN:
+    // "Event type - A generic Event with no added properties."
+    const event = new shaka.util.FakeEvent('abort');
+    if (this.onabort) {
+      this.onabort(event);
+    }
+    this.dispatchEvent(event);
+  }
+
+
+  /**
+   * @param {*=} reason
+   * @return {!AbortSignal}
+   */
+  static abort(reason) {
+    const signal = new shaka.polyfill.AbortController.AbortSignal();
+    signal.doAbort_(reason);
+    return signal;
+  }
+
+  /**
+   * @param {number} timeMs
+   * @return {!AbortSignal}
+   */
+  static timeout(timeMs) {
+    const signal = new shaka.polyfill.AbortController.AbortSignal();
+
+    window.setTimeout(() => {
+      // This is equivalent to a native implementation.
+      signal.doAbort_(new DOMException('signal timed out', 'TimeoutError'));
+    }, timeMs);
+
+    return signal;
+  }
+};
+
+
+shaka.polyfill.register(shaka.polyfill.AbortController.install);

shaka-player.uncompiled.js

@@ -32,6 +32,7 @@ goog.require('shaka.offline.OfflineManifestParser');
 goog.require('shaka.offline.OfflineScheme');
 goog.require('shaka.offline.Storage');
 goog.require('shaka.offline.indexeddb.StorageMechanism');
+goog.require('shaka.polyfill.AbortController');
 goog.require('shaka.polyfill.Aria');
 goog.require('shaka.polyfill.EncryptionScheme');
 goog.require('shaka.polyfill.Fullscreen');