Optimization for RTCQuicTransport- buffering CHLO.

If signaling arrives late on the server side of the RTCQuicTransport it
can be started after a CHLO has been received. This optimization buffers
the CHLO packet, so that the server doesn't need to wait another half
RTT + timeout for QUIC to retransmit the CHLO.

Bug: 874296
Change-Id: Iab35c1f5dba29cd2deaf5446a2d06d6990fe57f6
Reviewed-on: https://chromium-review.googlesource.com/c/1404433
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Steve Anton <steveanton@chromium.org>
Commit-Queue: Seth Hampson <shampson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622287}
6 files changed