Use SendTimeHistory to keep track of send times in simulations.

Use SendTimeHistory to keep track of send times in simulations.
Keep piggybacking send time in PacketInfo for now but use history in
order to be more in line with what we expect to do.

Landing this for sprang@. Original CL: https://review.webrtc.org/43559004/

TBR=sprang@webrtc.org
BUG=4308

Review URL: https://webrtc-codereview.appspot.com/48569004

Cr-Commit-Position: refs/heads/master@{#8778}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8778 4adac7df-926f-26a2-2b94-8c16560cd09d
10 files changed