Landing Recent QUIC changes until Thu Apr 20 2017

Convert QUIC non-feature flags to the old syntax, for consistency.

Merge internal change: 153720286
https://codereview.chromium.org/2828163005/

Increases inflight limit for QUIC BBR if the ack rate in the past half-rtt was  lower than half the current bandwidth estimate.

Protected by FLAGS_quic_reloadable_flag_quic_bbr_slow_recent_delivery.

Merge internal change: 153663187
https://codereview.chromium.org/2833673006/

Include unistd.h in quic_socket_utils.cc

Merge internal change: 153540629
https://codereview.chromium.org/2835473003/

Remain in packet conservation mode if BBR is in PROBE_BW and not in high-gain mode.  Protected by FLAGS_quic_reloadable_flag_quic_bbr_extra_conservation.

Merge internal change: 153506591
https://codereview.chromium.org/2832003002/

Review-Url: https://codereview.chromium.org/2834723002
Cr-Commit-Position: refs/heads/master@{#466169}
14 files changed