This was actually an older change to the Streams spec that we missed
when we implemented TransformStreams. This fixes a crash in the imported
WPT tests.
See: 007d729
This required a bit of manual manipulation. These tests dynamically
fetch generated IDL files, e.g.:
https://github.com/web-platform-tests/wpt/blob/master/interfaces/streams.idl
Our WPT importer is not able to detect the IDL files that need to be
imported, so dom.idl and streams.idl was copied over manually. Further,
idlharness.js would create URLs of the form "file://interfaces/dom.idl".
So idlharness.js was adapted to create a URL relative to the test file.
This widens the assertion from only checking if the WritableStream's
state is Errored or Erroring to asserting that the WritableStream is not
in a Writable state.
Our existing implementation of stream piping was extremely ad-hoc. It
did nothing to handle closed/errored streams, and did not read from or
write to streams in a way required by the spec.
This new implementation uses a custom JS::Cell to drive the read/write
loop.
These changes make sure that we postpone calls to
ReadableByteStreamControllerCommitPullIntoDescriptor until after all
pull-into descriptors have been filled up by
ReadableByteStreamControllerProcessPullIntoDescriptorsUsingQueue.
Also pulls in the WPT test which was created in relation to this spec
change. The test verifies that a patched then() will see a null
byobRequest.
