Replace assert_promise_rejects with upstream promise_rejects.

third_party/WebKit/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. 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);
-      }
-    });
-}
-
 // 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
 // object because we're in the middle of moving the attribute to a prototype
 // chain.  Once we complete the transition to prototype chains,
 // assert_will_be_idl_attribute must be replaced with assert_idl_attribute
 // defined in testharness.js.
 //
 // FIXME: Remove assert_will_be_idl_attribute once we complete the transition
 // of moving the DOM attributes to prototype chains.  (http://crbug.com/43394)
 function assert_will_be_idl_attribute(object, attribute_name, description) {

[jsbell, 2016/04/29 17:39:07]

aside: we can probably remove this now (separate CL)

[jsbell, 2016/04/29 19:09:41]

https://codereview.chromium.org/1936533003/

   assert_true(typeof object === "object", description);
 
   assert_true("hasOwnProperty" in object, description);
 
   // Do not test if |attribute_name| is not an own property because
   // |attribute_name| is in the middle of the transition to a prototype
   // chain.  (http://crbug.com/43394)
 
   assert_true(attribute_name in object, description);
 }
 
 // Stringifies a DOM object.  This function stringifies not only own properties
 // but also DOM attributes which are on a prototype chain.  Note that
 // JSON.stringify only stringifies own properties.
 function stringifyDOMObject(object)

[jsbell, 2016/04/29 17:39:07]

aside: code search tells me there is now just one use of this. we should remove
(separate CL)

[jsbell, 2016/04/29 21:16:42]

https://codereview.chromium.org/1935703003

 {
     function deepCopy(src) {
         if (typeof src != "object")
             return src;
         var dst = Array.isArray(src) ? [] : {};
         for (var property in src) {
             dst[property] = deepCopy(src[property]);
         }
         return dst;
     }
     return JSON.stringify(deepCopy(object));
 }