This CL prepares for adding the BBR network controller and
unit tests for GoogCC network controller.
The changes include:
* Adding pad_rate helper method on PacerConfig.
* Adding ostream operators for controller feedback structs.
* Adding increment operator to Timestamp class.
* Adding kEpoch to Timestamp class to represent 0.
* Rounding when multiplying with double.
Bug: webrtc:8415
Change-Id: I58289f37a6f9f2eee0a88bb06fb24dc295942862
Reviewed-on: https://webrtc-review.googlesource.com/61503
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22458}
