Move promise_test and assert_promise_rejects out of worker-test-harness.

LayoutTests/http/tests/resources/testharness-helpers.js

+/*
+ * testharness-helpers contains various useful extensions to testharness.js to
+ * allow them to be used across multiple tests before they have been
+ * upstreamed.

[asanka, 2014/10/10 19:39:11]

Could you mention here that testharness-helpers.js is intended to be usable from
both document and worker environments? Adding anything here that relies on the
DOM will likely break things on the worker tests. But it's good to have that
limitation be spelled out explicitly rather than be left to be discovered by
test failures.

[Marijn Kruisselbrink, 2014/10/10 20:32:55]

Done.

+ */
+
+// 'promise_test' is a new kind of testharness test that handles some
+// boilerplate for testing with promises.
+function promise_test(func, name, properties) {
+  properties = properties || {};
+  var test = async_test(name, properties);
+  Promise.resolve(test.step(func, test, test))
+    .then(function() { test.done(); })
+    .catch(test.step_func(function(value) {
+        throw value;
+      }));
+}
+
+// Returns a promise that fulfills after the provided |promise| is fulfilled.
+// The |test| succeeds only if |promise| rejects with an exception matching
+// |code|. Accepted values for |code| follow those accepted for assert_throws().
+// The optional |description| describes the test being performed.
+// E.g.:
+//   assert_promise_rejects(
+//       new Promise(...), // something that should throw an exception.
+//       'NotFoundError',
+//       'Should throw NotFoundError.');
+//
+//   assert_promise_rejects(
+//       new Promise(...),
+//       new TypeError(),
+//       'Should throw TypeError');
+function assert_promise_rejects(promise, code, description) {
+  return promise.then(
+    function() {
+      throw 'assert_promise_rejects: ' + description + ' Promise did not throw.';

[asanka, 2014/10/10 19:39:11]

Nit: 'Promise did not reject.'

[Marijn Kruisselbrink, 2014/10/10 20:32:55]

Done.

+    },
+    function(e) {
+      if (code !== undefined) {
+        assert_throws(code, function() { throw e; }, description);
+      }
+    });
+}