Create a new QUIC BBR ack aggregation patch which allows extra CWND only when bytes in flight has g…

Create a new QUIC BBR ack aggregation patch which allows extra CWND only when bytes in flight has gone below the target bytes in flight recently.  Protected by FLAGS_quic_reloadable_flag_quic_bbr_ack_aggregation_bytes2.

Merge internal change: 160232114

R=rch@chromium.org

[wangyix1, 2017-06-29 01:23:55]

The CQ bit was checked by wangyix@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-29 01:24:16]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Ryan Hamilton, 2017-06-29 02:55:37]

lgtm

[commit-bot: I haz the power, 2017-06-29 03:58:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-06-29 03:59:00]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[wangyix1, 2017-06-29 19:42:09]

The CQ bit was checked by wangyix@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-06-29 19:42:34]

Dry run: CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-06-29 21:07:41]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-06-29 21:07:42]

Dry run: This issue passed the CQ dry run.