Move congestion controller processing to the pacer thread.

webrtc/modules/pacing/alr_detector.cc

Index: webrtc/modules/pacing/alr_detector.cc
diff --git a/webrtc/modules/pacing/alr_detector.cc b/webrtc/modules/pacing/alr_detector.cc
index b31d4482bba37896bb7b0709d7e796d6e8c6eb53..997fd130985f4d2f6a608367dd7801f78fec932f 100644
--- a/webrtc/modules/pacing/alr_detector.cc
+++ b/webrtc/modules/pacing/alr_detector.cc
@@ -36,6 +36,8 @@ AlrDetector::AlrDetector()
 AlrDetector::~AlrDetector() {}
 
 void AlrDetector::OnBytesSent(size_t bytes_sent, int64_t now_ms) {
+  // TODO(nisse): It's unclear what guarantees there are that this

[danilchap, 2017/01/16 17:09:39]

might be better to write TODO by specifying what should be done and, if
applicable, when it should be done.
If comment can't be phrased in such a way, may it is not a TODO, but just a
comment.

[nisse-webrtc, 2017/01/17 07:42:39]

I'll try to rephrase it. The need action is to document the guarantee, if one
exists, or else remove the DCHECK.

+  // function isn't called before SetEstimatedBitrate.
   RTC_DCHECK(estimated_bitrate_bps_);
 
   rate_.Update(bytes_sent, now_ms);