There is a difference between the reference implementation and the Chromium implementation that causes the upstream version of the test to fail. Chromium has a copy of the test that tests Chromium's implementation.
Once https://github.com/whatwg/streams/pull/634 is resolved and the changes are merged into Chromium the difference will go away and Chromium's version of the test should be deleted.
Comment 1 by ricea@chromium.org
, Apr 6 2017