Set min BWE bitrate form 10kbps to 5kbps and centralize minimum bitrate.

webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h

Index: webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h
diff --git a/webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h b/webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h
index dfeedfce853ac542d22ff89b970f19ed36bca232..29dd81bf27bb7c1e68faaf87e92654507b0ac6af 100644
--- a/webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h
+++ b/webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h
@@ -44,7 +44,6 @@ struct ReceiveBandwidthEstimatorStats {};
 
 class RemoteBitrateEstimator : public CallStatsObserver, public Module {
  public:
-  static const int kDefaultMinBitrateBps = 30000;

[minyue-webrtc, 2016/10/13 08:12:31]

why not merging all to this.

[michaelt, 2016/10/13 09:38:41]

I did it in the bwe_defines.h so that i not have to include the
remote_bitrate_estimator.h in the other files.
But i don't have a relay strong opinion on that. If you think we should use
RemoteBitrateEstimator::kDefaultMinBitrateBps it would be fine to me as well.

[stefan-webrtc, 2016/10/17 18:05:04]

I would prefer if we move the min/max bitrates to
modules/congestion_controller/. Maybe a defines.h under
congestion_controller/include/?

The namespace could be "congestion_controller" or something like that.

[michaelt, 2016/10/25 09:40:56]

Done.

   virtual ~RemoteBitrateEstimator() {}
 
   virtual void IncomingPacketFeedbackVector(