Add support for updating histogram for received fraction loss ("WebRTC.Video.ReceivedPacketsLostInPercent") when running new video api.

Add tests for verifying that video histograms are updated.

BUG=
R=pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/44309004

Cr-Commit-Position: refs/heads/master@{#9085}