QUIC refactor CL to move some methods and give the QuicSentPacketManager
control over when the retransmission alarm is reset.

Merge internal change: 58352761

R=rch@chromium.org

Review URL: https://codereview.chromium.org/118443007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242808 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242808