Streams tests try to call ReadableStream.prototype.pipeThrough.call generically ReadableStream methods are nowadays defined to accept only ReadableStream instances. Tests sometimes assert that an exception is thrown. However, the exception being actually thrown is different. Future testharness.js will check the exception and the test will fail.
Created attachment 449901 [details] Patch
Comment on attachment 449901 [details] Patch r=me, all these tests are older versions of tests that we run in LayoutTests/imported/w3c/web-platform-tests/streams folder/subfolders
Committed r288611 (246430@main): <https://commits.webkit.org/246430@main> All reviewed patches have been landed. Closing bug and clearing flags on attachment 449901 [details].
<rdar://problem/88065943>