Replace assert_promise_rejects with upstream promise_rejects.

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

Index: third_party/WebKit/LayoutTests/http/tests/resources/testharness-helpers.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/resources/testharness-helpers.js b/third_party/WebKit/LayoutTests/http/tests/resources/testharness-helpers.js
index 12960e30ac8ce9423dc11c7bea9841cec950f012..9d84557c0555a6592cdd0ce9fa55ee09af1fd6e8 100644
--- a/third_party/WebKit/LayoutTests/http/tests/resources/testharness-helpers.js
+++ b/third_party/WebKit/LayoutTests/http/tests/resources/testharness-helpers.js
@@ -5,33 +5,6 @@
  * 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);
-      }
-    });
-}
-
 // Asserts that |object| that is an instance of some interface has the attribute
 // |attribute_name| following the conditions specified by WebIDL, but it's
 // acceptable that the attribute |attribute_name| is an own property of the