1 files changed, 93 insertions, 0 deletions
diff --git a/js/src/tests/web-platform-test-shims.js b/js/src/tests/web-platform-test-shims.js
new file mode 100644
index 0000000000..97122ab860
--- /dev/null
+++ b/js/src/tests/web-platform-test-shims.js
@@ -0,0 +1,93 @@
+// This is used when jstests.py runs web-platform-tests in the shell.
+// Some tests require browser features that the shell doesn't have built-in.
+
+// window.self
+// <https://html.spec.whatwg.org/multipage/window-object.html#dom-self>
+if (!("self" in this)) {
+  this.self = this;
+}
+
+// window.setTimeout, clearTimeout, setInterval, clearInterval
+// <https://html.spec.whatwg.org/multipage/timers-and-user-prompts.html#dom-settimeout>
+if (!("setTimeout" in this)) {
+  // Not-very-compliant polyfill for setTimeout, based on Promise.
+
+  // When this array becomes non-empty, call scheduleWork.
+  let timeouts = [];
+
+  // Fake clock used to order timeouts.
+  let now = 0;
+
+  // Least positive integer not yet used as a timer id.
+  let next_id = 1;
+
+  // Add an active timer record to timeouts.
+  function enqueue(id, t, cb) {
+    if (typeof cb !== 'function') {
+      let code = "" + cb;
+      cb = () => eval(code);
+    }
+    t += now;
+    timeouts.push({id, t, cb});
+    timeouts.sort((a, b) => a.t - b.t);
+    if (timeouts.length === 1) {
+      scheduleWork();
+    }
+  }
+
+  // Register a microtask to make sure timers are actually processed. There
+  // should be at most one of these microtasks pending at a time.
+  function scheduleWork() {
+    // Number of times to let the microtask queue spin before running a
+    // timeout. The idea is to let all Promises resolve between consecutive
+    // timer callbacks. Of course, this is a hack; whatever number is used
+    // here, an async function can simply await that many times plus one to
+    // observe that timeouts are being handled as microtasks, not events.
+    let delay = 10;
+
+    function handleTimeouts() {
+      if (--delay > 0) {
+        Promise.resolve().then(handleTimeouts);
+        return;
+      }
+      if (timeouts.length > 0) {
+        let {t, cb} = timeouts.shift();
+        if (now < t) {
+          now = t;
+        }
+        if (timeouts.length > 0) {
+          scheduleWork();  // There's more to do after this.
+        }
+        cb();
+      }
+    }
+    Promise.resolve().then(handleTimeouts);
+  }
+
+  this.setTimeout = function (cb, t, ...args) {
+    let id = next_id++;
+    enqueue(id, t, () => cb(...args));
+    return id;
+  };
+
+  this.clearTimeout = function (id) {
+    timeouts = timeouts.filter(obj => obj.id !== id);
+  };
+
+  this.setInterval = function (cb, t, ...args) {
+    let id = next_id++;
+    let func = () => {
+      enqueue(id, t, func);
+      cb(...args);
+    };
+    enqueue(id, t, func);
+    return id;
+  };
+
+  this.clearInterval = this.clearTimeout;
+}
+
+// Some tests in web platform tests leave promise rejections unhandled.
+if ("ignoreUnhandledRejections" in this) {
+  ignoreUnhandledRejections();
+}