Ensure that BBR does not drop to exceedingly low pacing rates during the STARTUP phase. Protected …

Ensure that BBR does not drop to exceedingly low pacing rates during the STARTUP phase.  Protected by FLAGS_quic_bbr_faster_startup.

This is ensured in two ways:
- The pacing rate is never decreased during the STARTUP phase.
- The pacing rate is set to be at least initial_window / min_rtt.

Merge internal change: 140102880

BUG=

[Ryan Hamilton, 2016-12-01 21:15:57]

rch@chromium.org changed reviewers:
+ zhongyi@chromium.org

[Zhongyi Shi, 2016-12-01 22:45:46]

lgtm

https://codereview.chromium.org/2542273002/diff/1/net/quic/core/quic_flags_li...
File net/quic/core/quic_flags_list.h (right):

https://codereview.chromium.org/2542273002/diff/1/net/quic/core/quic_flags_li...
net/quic/core/quic_flags_list.h:153: QUIC_FLAG(bool,
FLAGS_quic_bbr_faster_startup, true)
Please make sure the default value is correct since the internal is still off.

[Zhongyi Shi, 2016-12-01 22:51:45]

https://codereview.chromium.org/2542273002/diff/1/net/quic/core/quic_flags_li...
File net/quic/core/quic_flags_list.h (right):

https://codereview.chromium.org/2542273002/diff/1/net/quic/core/quic_flags_li...
net/quic/core/quic_flags_list.h:153: QUIC_FLAG(bool,
FLAGS_quic_bbr_faster_startup, true)
On 2016/12/01 22:45:46, Zhongyi Shi wrote:
> Please make sure the default value is correct since the internal is still off.

okay, it's flipped to false in the flag flip cl.