[webtransport] opening a bidirectional stream triggers exception

[phsultan]

From the test page https://googlechrome.github.io/samples/webtransport/client.html, when opening a bidirectional webtransport stream, an exception is triggered that prevents from receiving data from the server.

To reproduce, from https://googlechrome.github.io/samples/webtransport/client.html

• connect to your webtransport server
• enter some content in the textarea input, select Open a bidirectional stream then click Send data

result:

• a bidirectional webtransport stream is established, data can be sent but not received
• in the JS console, the exception below is triggered:
  Uncaught (in promise) TypeError: stream.pipeThrough is not a function

what is expected:

• a bidirectional webtransport stream is established, data can be sent and received and no exception is shown in the JS console (I'm testing with a simple webtransport server that echoes back any received data)