Land Recent QUIC Changes.

Disable QUIC pacing until a valid RTT estimate has been recevied.

Merge internal change: 59820552
https://codereview.chromium.org/135053008/


Change QuicConnection::WritePacket so it takes a const& instead of *
to QuicPacket.

Merge internal change: 59820019
https://codereview.chromium.org/143693002/


Implement TCP proportional rate reduction in QUIC's TCP style
congestion control.

Merge internal change: 59685915
https://codereview.chromium.org/135183006/


Fix QUIC's implementation of Cubic and Reno to not increase the CWND
during recovery.

This was causing QUIC to be overly aggressive and in practice have a
minimum CWND of 12, since it raised the CWND before a loss could be
registered.

Merge internal change: 59615701
https://codereview.chromium.org/143083004/

R=rch@chromium.org

Review URL: https://codereview.chromium.org/130703009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246105 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246105
Documentation fix - Delete meaningless paragraph.

BUG=none

Review URL: https://codereview.chromium.org/135903010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@246106 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 246106