Import wpt@503f5b5f78ec4e87d144f78609f363f0ed0ea8db

third_party/WebKit/LayoutTests/external/wpt/html/webappapis/scripting/processing-model-2/unhandled-promise-rejections/support/promise-rejection-events.js

Index: third_party/WebKit/LayoutTests/external/wpt/html/webappapis/scripting/processing-model-2/unhandled-promise-rejections/support/promise-rejection-events.js
diff --git a/third_party/WebKit/LayoutTests/external/wpt/html/webappapis/scripting/processing-model-2/unhandled-promise-rejections/support/promise-rejection-events.js b/third_party/WebKit/LayoutTests/external/wpt/html/webappapis/scripting/processing-model-2/unhandled-promise-rejections/support/promise-rejection-events.js
new file mode 100644
index 0000000000000000000000000000000000000000..0de39f695ab6381aa2216cbb37a6427d94b6043d
--- /dev/null
+++ b/third_party/WebKit/LayoutTests/external/wpt/html/webappapis/scripting/processing-model-2/unhandled-promise-rejections/support/promise-rejection-events.js
@@ -0,0 +1,900 @@
+'use strict';
+
+if (self.importScripts) {
+  importScripts('/resources/testharness.js');
+}
+
+setup({
+  allow_uncaught_exception: true
+});
+
+//
+// Straightforward unhandledrejection tests
+//
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.reject(e);
+}, 'unhandledrejection: from Promise.reject');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = new Promise(function(_, reject) {
+    reject(e);
+  });
+}, 'unhandledrejection: from a synchronous rejection in new Promise');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = new Promise(function(_, reject) {
+    postMessageTask(function() {
+      reject(e);
+    });
+  });
+}, 'unhandledrejection: from a task-delayed rejection');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = new Promise(function(_, reject) {
+    setTimeout(function() {
+      reject(e);
+    }, 1);
+  });
+}, 'unhandledrejection: from a setTimeout-delayed rejection');
+
+async_test(function(t) {
+  var e = new Error();
+  var e2 = new Error();
+  var promise2;
+
+  onUnhandledSucceed(t, e2, function() { return promise2; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  promise2 = Promise.reject(e).then(unreached, function(reason) {
+    t.step(function() {
+      assert_equals(reason, e);
+    });
+    throw e2;
+  });
+}, 'unhandledrejection: from a throw in a rejection handler chained off of Promise.reject');
+
+async_test(function(t) {
+  var e = new Error();
+  var e2 = new Error();
+  var promise2;
+
+  onUnhandledSucceed(t, e2, function() { return promise2; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  promise2 = new Promise(function(_, reject) {
+    setTimeout(function() {
+      reject(e);
+    }, 1);
+  }).then(unreached, function(reason) {
+    t.step(function() {
+      assert_equals(reason, e);
+    });
+    throw e2;
+  });
+}, 'unhandledrejection: from a throw in a rejection handler chained off of a setTimeout-delayed rejection');
+
+async_test(function(t) {
+  var e = new Error();
+  var e2 = new Error();
+  var promise2;
+
+  onUnhandledSucceed(t, e2, function() { return promise2; });
+
+  var promise = new Promise(function(_, reject) {
+    setTimeout(function() {
+      reject(e);
+      mutationObserverMicrotask(function() {
+        var unreached = t.unreached_func('promise should not be fulfilled');
+        promise2 = promise.then(unreached, function(reason) {
+          t.step(function() {
+            assert_equals(reason, e);
+          });
+          throw e2;
+        });
+      });
+    }, 1);
+  });
+}, 'unhandledrejection: from a throw in a rejection handler attached one microtask after a setTimeout-delayed rejection');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.resolve().then(function() {
+    return Promise.reject(e);
+  });
+}, 'unhandledrejection: from returning a Promise.reject-created rejection in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.resolve().then(function() {
+    throw e;
+  });
+}, 'unhandledrejection: from a throw in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.resolve().then(function() {
+    return new Promise(function(_, reject) {
+      setTimeout(function() {
+        reject(e);
+      }, 1);
+    });
+  });
+}, 'unhandledrejection: from returning a setTimeout-delayed rejection in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.all([Promise.reject(e)]);
+}, 'unhandledrejection: from Promise.reject, indirected through Promise.all');
+
+//
+// Negative unhandledrejection/rejectionhandled tests with immediate attachment
+//
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = Promise.reject(e).then(unreached, function() {});
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a promise from Promise.reject');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = Promise.all([Promise.reject(e)]).then(unreached, function() {});
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a promise from ' +
+   'Promise.reject, indirecting through Promise.all');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = new Promise(function(_, reject) {
+    reject(e);
+  }).then(unreached, function() {});
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a synchronously-rejected ' +
+   'promise created with new Promise');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = Promise.resolve().then(function() {
+    throw e;
+  }).then(unreached, function(reason) {
+    t.step(function() {
+      assert_equals(reason, e);
+    });
+  });
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a promise created from ' +
+   'throwing in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = Promise.resolve().then(function() {
+    return Promise.reject(e);
+  }).then(unreached, function(reason) {
+    t.step(function() {
+      assert_equals(reason, e);
+    });
+  });
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a promise created from ' +
+   'returning a Promise.reject-created promise in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  var unreached = t.unreached_func('promise should not be fulfilled');
+  p = Promise.resolve().then(function() {
+    return new Promise(function(_, reject) {
+      setTimeout(function() {
+        reject(e);
+      }, 1);
+    });
+  }).then(unreached, function(reason) {
+    t.step(function() {
+      assert_equals(reason, e);
+    });
+  });
+}, 'no unhandledrejection/rejectionhandled: rejection handler attached synchronously to a promise created from ' +
+   'returning a setTimeout-delayed rejection in a fulfillment handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  postMessageTask(function() {
+    p = Promise.resolve().then(function() {
+      return Promise.reject(e);
+    })
+    .catch(function() {});
+  });
+}, 'no unhandledrejection/rejectionhandled: all inside a queued task, a rejection handler attached synchronously to ' +
+   'a promise created from returning a Promise.reject-created promise in a fulfillment handler');
+
+//
+// Negative unhandledrejection/rejectionhandled tests with microtask-delayed attachment
+//
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  p = Promise.reject(e);
+  mutationObserverMicrotask(function() {
+    var unreached = t.unreached_func('promise should not be fulfilled');
+    p.then(unreached, function() {});
+  });
+}, 'delayed handling: a microtask delay before attaching a handler prevents both events (Promise.reject-created ' +
+   'promise)');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  p = new Promise(function(_, reject) {
+    reject(e);
+  });
+  mutationObserverMicrotask(function() {
+    var unreached = t.unreached_func('promise should not be fulfilled');
+    p.then(unreached, function() {});
+  });
+}, 'delayed handling: a microtask delay before attaching a handler prevents both events (immediately-rejected new ' +
+   'Promise-created promise)');
+
+async_test(function(t) {
+  var e = new Error();
+  var p1;
+  var p2;
+
+  onUnhandledFail(t, function() { return p1; });
+  onUnhandledFail(t, function() { return p2; });
+
+  p1 = new Promise(function(_, reject) {
+    mutationObserverMicrotask(function() {
+      reject(e);
+    });
+  });
+  p2 = Promise.all([p1]);
+  mutationObserverMicrotask(function() {
+    var unreached = t.unreached_func('promise should not be fulfilled');
+    p2.then(unreached, function() {});
+  });
+}, 'delayed handling: a microtask delay before attaching the handler, and before rejecting the promise, indirected ' +
+   'through Promise.all');
+
+//
+// Negative unhandledrejection/rejectionhandled tests with nested-microtask-delayed attachment
+//
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  p = Promise.reject(e);
+  mutationObserverMicrotask(function() {
+    Promise.resolve().then(function() {
+      mutationObserverMicrotask(function() {
+        Promise.resolve().then(function() {
+          p.catch(function() {});
+        });
+      });
+    });
+  });
+}, 'microtask nesting: attaching a handler inside a combination of mutationObserverMicrotask + promise microtasks');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  postMessageTask(function() {
+    p = Promise.reject(e);
+    mutationObserverMicrotask(function() {
+      Promise.resolve().then(function() {
+        mutationObserverMicrotask(function() {
+          Promise.resolve().then(function() {
+            p.catch(function() {});
+          });
+        });
+      });
+    });
+  });
+}, 'microtask nesting: attaching a handler inside a combination of mutationObserverMicrotask + promise microtasks, ' +
+   'all inside a postMessageTask');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  setTimeout(function() {
+    p = Promise.reject(e);
+    mutationObserverMicrotask(function() {
+      Promise.resolve().then(function() {
+        mutationObserverMicrotask(function() {
+          Promise.resolve().then(function() {
+            p.catch(function() {});
+          });
+        });
+      });
+    });
+  }, 0);
+}, 'microtask nesting: attaching a handler inside a combination of mutationObserverMicrotask + promise microtasks, ' +
+   'all inside a setTimeout');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  p = Promise.reject(e);
+  Promise.resolve().then(function() {
+    mutationObserverMicrotask(function() {
+      Promise.resolve().then(function() {
+        mutationObserverMicrotask(function() {
+          p.catch(function() {});
+        });
+      });
+    });
+  });
+}, 'microtask nesting: attaching a handler inside a combination of promise microtasks + mutationObserverMicrotask');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  postMessageTask(function() {
+    p = Promise.reject(e);
+    Promise.resolve().then(function() {
+      mutationObserverMicrotask(function() {
+        Promise.resolve().then(function() {
+          mutationObserverMicrotask(function() {
+            p.catch(function() {});
+          });
+        });
+      });
+    });
+  });
+}, 'microtask nesting: attaching a handler inside a combination of promise microtasks + mutationObserverMicrotask, ' +
+   'all inside a postMessageTask');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledFail(t, function() { return p; });
+
+  setTimeout(function() {
+    p = Promise.reject(e);
+    Promise.resolve().then(function() {
+      mutationObserverMicrotask(function() {
+        Promise.resolve().then(function() {
+          mutationObserverMicrotask(function() {
+            p.catch(function() {});
+          });
+        });
+      });
+    });
+  }, 0);
+}, 'microtask nesting: attaching a handler inside a combination of promise microtasks + mutationObserverMicrotask, ' +
+   'all inside a setTimeout');
+
+
+// For workers, postMessageTask() involves posting tasks to other threads, so
+// the following tests don't work there.
+
+if ('document' in self) {
+  //
+  // Negative unhandledrejection/rejectionhandled tests with task-delayed attachment
+  //
+
+  async_test(function(t) {
+    var e = new Error();
+    var p;
+
+    onUnhandledFail(t, function() { return p; });
+
+    var _reject;
+    p = new Promise(function(_, reject) {
+      _reject = reject;
+    });
+    _reject(e);
+    postMessageTask(function() {
+      var unreached = t.unreached_func('promise should not be fulfilled');
+      p.then(unreached, function() {});
+    });
+  }, 'delayed handling: a task delay before attaching a handler prevents unhandledrejection');
+
+  async_test(function(t) {
+    var e = new Error();
+    var p;
+
+    onUnhandledFail(t, function() { return p; });
+
+    p = Promise.reject(e);
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        p.catch(function() {});
+      });
+    });
+  }, 'delayed handling: postMessageTask after promise creation/rejection, plus promise microtasks, is not too late to ' +
+     'attach a rejection handler');
+
+  async_test(function(t) {
+    var e = new Error();
+    var p;
+
+    onUnhandledFail(t, function() { return p; });
+
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        Promise.resolve().then(function() {
+          Promise.resolve().then(function() {
+            Promise.resolve().then(function() {
+              p.catch(function() {});
+            });
+          });
+        });
+      });
+    });
+    p = Promise.reject(e);
+  }, 'delayed handling: postMessageTask before promise creation/rejection, plus many promise microtasks, is not too ' +
+     'late to attach a rejection handler');
+
+  async_test(function(t) {
+    var e = new Error();
+    var p;
+
+    onUnhandledFail(t, function() { return p; });
+
+    p = Promise.reject(e);
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        Promise.resolve().then(function() {
+          Promise.resolve().then(function() {
+            Promise.resolve().then(function() {
+              p.catch(function() {});
+            });
+          });
+        });
+      });
+    });
+  }, 'delayed handling: postMessageTask after promise creation/rejection, plus many promise microtasks, is not too ' +
+     'late to attach a rejection handler');
+}
+
+//
+// Positive unhandledrejection/rejectionhandled tests with delayed attachment
+//
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  var _reject;
+  p = new Promise(function(_, reject) {
+    _reject = reject;
+  });
+  _reject(e);
+  postMessageTask(function() {
+    postMessageTask(function() {
+      var unreached = t.unreached_func('promise should not be fulfilled');
+      p.then(unreached, function() {});
+    });
+  });
+}, 'delayed handling: a nested-task delay before attaching a handler causes unhandledrejection');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.reject(e);
+  postMessageTask(function() {
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        p.catch(function() {});
+      });
+    });
+  });
+}, 'delayed handling: a nested-postMessageTask after promise creation/rejection, plus promise microtasks, is too ' +
+   'late to attach a rejection handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  postMessageTask(function() {
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        Promise.resolve().then(function() {
+          Promise.resolve().then(function() {
+            Promise.resolve().then(function() {
+              p.catch(function() {});
+            });
+          });
+        });
+      });
+    });
+  });
+  p = Promise.reject(e);
+}, 'delayed handling: a nested-postMessageTask before promise creation/rejection, plus many promise microtasks, is ' +
+   'too late to attach a rejection handler');
+
+async_test(function(t) {
+  var e = new Error();
+  var p;
+
+  onUnhandledSucceed(t, e, function() { return p; });
+
+  p = Promise.reject(e);
+  postMessageTask(function() {
+    postMessageTask(function() {
+      Promise.resolve().then(function() {
+        Promise.resolve().then(function() {
+          Promise.resolve().then(function() {
+            Promise.resolve().then(function() {
+              p.catch(function() {});
+            });
+          });
+        });
+      });
+    });
+  });
+}, 'delayed handling: a nested-postMessageTask after promise creation/rejection, plus many promise microtasks, is ' +
+   'too late to attach a rejection handler');
+
+async_test(function(t) {
+  var unhandledPromises = [];
+  var unhandledReasons = [];
+  var e = new Error();
+  var p;
+
+  var unhandled = function(ev) {
+    if (ev.promise === p) {
+      t.step(function() {
+        unhandledPromises.push(ev.promise);
+        unhandledReasons.push(ev.reason);
+      });
+    }
+  };
+  var handled = function(ev) {
+    if (ev.promise === p) {
+      t.step(function() {
+        assert_array_equals(unhandledPromises, [p]);
+        assert_array_equals(unhandledReasons, [e]);
+        assert_equals(ev.promise, p);
+        assert_equals(ev.reason, e);
+      });
+    }
+  };
+  addEventListener('unhandledrejection', unhandled);
+  addEventListener('rejectionhandled', handled);
+  ensureCleanup(t, unhandled, handled);
+
+  p = new Promise(function() {
+    throw e;
+  });
+  setTimeout(function() {
+    var unreached = t.unreached_func('promise should not be fulfilled');
+    p.then(unreached, function(reason) {
+      assert_equals(reason, e);
+      setTimeout(function() { t.done(); }, 10);
+    });
+  }, 10);
+}, 'delayed handling: delaying handling by setTimeout(,10) will cause both events to fire');
+
+//
+// Miscellaneous tests about integration with the rest of the platform
+//
+
+async_test(function(t) {
+  var e = new Error();
+  var l = function(ev) {
+    var order = [];
+    mutationObserverMicrotask(function() {
+      order.push(1);
+    });
+    setTimeout(function() {
+      order.push(2);
+      t.step(function() {
+        assert_array_equals(order, [1, 2]);
+      });
+      t.done();
+    }, 1);
+  };
+  addEventListener('unhandledrejection', l);
+  ensureCleanup(t, l);
+  Promise.reject(e);
+}, 'mutationObserverMicrotask vs. postMessageTask ordering is not disturbed inside unhandledrejection events');
+
+// For workers, postMessageTask() involves posting tasks to other threads, so
+// the following tests don't work there.
+
+if ('document' in self) {
+
+  // For the next two see https://github.com/domenic/unhandled-rejections-browser-spec/issues/2#issuecomment-121121695
+  // and the following comments.
+
+  async_test(function(t) {
+    var sequenceOfEvents = [];
+
+    addEventListener('unhandledrejection', l);
+    ensureCleanup(t, l);
+
+    var p1 = Promise.reject();
+    var p2;
+    postMessageTask(function() {
+      p2 = Promise.reject();
+      postMessageTask(function() {
+        sequenceOfEvents.push('postMessageTask');
+        checkSequence();
+      });
+    });
+
+    function l(ev) {
+      if (ev.promise === p1 || ev.promise === p2) {
+        sequenceOfEvents.push(ev.promise);
+        checkSequence();
+      }
+    }
+
+    function checkSequence() {
+      if (sequenceOfEvents.length === 3) {
+        t.step(function() {
+          assert_array_equals(sequenceOfEvents, [p1, 'postMessageTask', p2]);
+        });
+        t.done();
+      }
+    }
+  }, 'postMessageTask ordering vs. the task queued for unhandled rejection notification (1)');
+
+  async_test(function(t) {
+    var sequenceOfEvents = [];
+
+    addEventListener('unhandledrejection', l);
+    ensureCleanup(t, l);
+
+    var p2;
+    postMessageTask(function() {
+      p2 = Promise.reject();
+      postMessageTask(function() {
+        sequenceOfEvents.push('postMessageTask');
+        checkSequence();
+      });
+    });
+
+    function l(ev) {
+      if (ev.promise == p2) {
+        sequenceOfEvents.push(ev.promise);
+        checkSequence();
+      }
+    }
+
+    function checkSequence() {
+      if (sequenceOfEvents.length === 2) {
+        t.step(function() {
+          assert_array_equals(sequenceOfEvents, ['postMessageTask', p2]);
+        });
+        t.done();
+      }
+    }
+  }, 'postMessageTask ordering vs. the task queued for unhandled rejection notification (2)');
+
+  async_test(function(t) {
+    var sequenceOfEvents = [];
+
+
+    addEventListener('unhandledrejection', unhandled);
+    addEventListener('rejectionhandled', handled);
+    ensureCleanup(t, unhandled, handled);
+
+    var p = Promise.reject();
+
+    setTimeout(function() {
+      postMessageTask(function() {
+        sequenceOfEvents.push('task before catch');
+        checkSequence();
+      });
+
+      p.catch(function() {
+        sequenceOfEvents.push('catch');
+        checkSequence();
+      });
+
+      postMessageTask(function() {
+        sequenceOfEvents.push('task after catch');
+        checkSequence();
+      });
+
+      sequenceOfEvents.push('after catch');
+      checkSequence();
+    }, 10);
+
+    function unhandled(ev) {
+      if (ev.promise === p) {
+        sequenceOfEvents.push('unhandled');
+        checkSequence();
+      }
+    }
+
+    function handled(ev) {
+      if (ev.promise === p) {
+        sequenceOfEvents.push('handled');
+        checkSequence();
+      }
+    }
+
+    function checkSequence() {
+      if (sequenceOfEvents.length === 6) {
+        t.step(function() {
+          assert_array_equals(sequenceOfEvents,
+            ['unhandled', 'after catch', 'catch', 'task before catch', 'handled', 'task after catch']);
+        });
+        t.done();
+      }
+    }
+  }, 'rejectionhandled is dispatched from a queued task, and not immediately');
+}
+
+//
+// HELPERS
+//
+
+var globalPostMessageCounter = 0;
+
+function postMessageTask(f) {
+  if ('document' in self) {
+    var message = 'abusingpostmessageforfunandprofit' + globalPostMessageCounter;
+    globalPostMessageCounter++;
+    var l = function(ev) {
+      if (ev.data === message) {
+        removeEventListener('message', l);
+        f();
+      }
+    };
+    addEventListener('message', l);
+    postMessage(message, '*');
+  } else {
+    var channel = new MessageChannel();
+    channel.port1.onmessage = function() { channel.port1.close(); f(); };
+    channel.port2.postMessage('abusingpostmessageforfunandprofit');
+    channel.port2.close();
+  }
+}
+
+function mutationObserverMicrotask(f) {
+  if ('document' in self) {
+    var observer = new MutationObserver(function() { f(); });
+    var node = document.createTextNode('');
+    observer.observe(node, { characterData: true });
+    node.data = 'foo';
+  } else {
+    // We don't have mutation observers on workers, so just post a promise-based
+    // microtask.
+    Promise.resolve().then(function() { f(); });
+  }
+}
+
+function onUnhandledSucceed(t, expectedReason, expectedPromiseGetter) {
+  var l = function(ev) {
+    if (ev.promise === expectedPromiseGetter()) {
+      t.step(function() {
+        assert_equals(ev.reason, expectedReason);
+        assert_equals(ev.promise, expectedPromiseGetter());
+      });
+      t.done();
+    }
+  };
+  addEventListener('unhandledrejection', l);
+  ensureCleanup(t, l);
+}
+
+function onUnhandledFail(t, expectedPromiseGetter) {
+  var unhandled = function(evt) {
+    if (evt.promise === expectedPromiseGetter()) {
+      t.step(function() {
+        assert_unreached('unhandledrejection event is not supposed to be triggered');
+      });
+    }
+  };
+  var handled = function(evt) {
+    if (evt.promise === expectedPromiseGetter()) {
+      t.step(function() {
+        assert_unreached('rejectionhandled event is not supposed to be triggered');
+      });
+    }
+  };
+  addEventListener('unhandledrejection', unhandled);
+  addEventListener('rejectionhandled', handled);
+  ensureCleanup(t, unhandled, handled);
+  setTimeout(function() {
+    t.done();
+  }, 10);
+}
+
+function ensureCleanup(t, unhandled, handled) {
+  t.add_cleanup(function() {
+    if (unhandled)
+      removeEventListener('unhandledrejection', unhandled);
+    if (handled)
+      removeEventListener('rejectionhandled', handled);
+  });
+}
+
+done();