Replace assert_promise_rejects with upstream promise_rejects.

third_party/WebKit/LayoutTests/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. This file is intended to be usable from both document and worker
- * environments, so code should for example not rely on the DOM.
- */
-
-// 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 reject.';
-    },
-    function(e) {
-      if (code !== undefined) {
-        assert_throws(code, function() { throw e; }, description);
-      }
-    });
-}