The patch from bug 1772205 has the following problem:
reads and rites are sometimes not triggered by the real socket or the lowest HTTP/2 session(the session to the proxy). This is a usual case when TLSFilter is used. The current implementation cannot read or write in this case, it will only call ResumeSend/Recv and TransactionHasDataToWrite/Read. I think this is unnecessarily restrictive:

• In the case of writing data to the network we can just write without waiting for HTTP/2 session to trigger writes. (We need to be careful to make sue that the buffer are not going too much, probably this is something that already works fine)
• In the case of read there are 2 situations:
  • a stream has buffered data: in this case we could just read from the buffer
  • a stream does not have buffered data: here we need to wait for the proxy session to callback when ithas more data.