Simplify FakeReceiveStatistics in video send stream tests

Rtcp sender now take smaller interface making it possible to simplify the fake

BUG=webrtc:8016

Review-Url: https://codereview.webrtc.org/2984283002
Cr-Original-Commit-Position: refs/heads/master@{#19181}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 901b2df431d9834910be5747df69960ce9830b70
1 file changed