This reverts commit 825eb58d59940a4c3c9837595c4b3b07059c93ca. This Relands the cl reviewed in https://codereview.webrtc.org/1917793002/ patchset #1 is a pure reland. patchset #2 fix an overflow in BitrateProber that caused WebRtcVideoChannel2BaseTest.TwoStreamsSendAndReceive to fail. Original cl description: Remove SendPacer from ViEEncoder This CL moves the logic where the ViEEncoder pause if the pacer is full to the BitrateController. If the queue is full, the controller reports a bitrate of zero to Call (and BitrateAllocator) R=stefan@webrtc.org TBR=mflodman@webrtc.org BUG=webrtc:5687 Review URL: https://codereview.webrtc.org/1947873002 . Cr-Commit-Position: refs/heads/master@{#12630}