tree e4b69318802b26d627ea63e30bdc8504a8b75fce
parent 8e9d94458d1ba68a1f1deb87b66c96d786905006
author bnc <bnc@google.com> 1570065043 -0700
committer Copybara-Service <copybara-worker@google.com> 1570131448 -0700

Fix QPACK crash by unregistering observers with QpackHeaderTable.

QpackHeaderTable is owned by QpackDecoder, owned by QuicSpdySession.  Each
observer is a QpackProgressiveDecoder, owned by QpackHeaderAccumulator, owned by
QuicSpdyStream.  If a stream is deleted (local cancellation, reset received from
peer), then the observer must be deregistered with QpackHeaderTable in order to
avoid a crash.

gfe-relnote: n/a, change to QUIC v99-only code.  Protected by existing disabled gfe2_reloadable_flag_quic_enable_version_99.
PiperOrigin-RevId: 272562981
Change-Id: Ia49f2ef9aeeebcccb83405107f0224ee7d23694f