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

webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc

Index: webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
index f83cddc617862b56ca50131895e97921084178b2..5fcf2ba92c104dda88015d52e12e0a8a79deddd8 100644
--- a/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
+++ b/webrtc/modules/remote_bitrate_estimator/aimd_rate_control.cc
@@ -17,6 +17,7 @@
 #include "webrtc/base/checks.h"
 
 #include "webrtc/modules/remote_bitrate_estimator/overuse_detector.h"
+#include "webrtc/modules/remote_bitrate_estimator/include/bwe_defines.h"
 #include "webrtc/modules/remote_bitrate_estimator/include/remote_bitrate_estimator.h"
 #include "webrtc/modules/remote_bitrate_estimator/test/bwe_test_logging.h"
 
@@ -28,7 +29,7 @@ static const int64_t kMaxFeedbackIntervalMs = 1000;
 
 AimdRateControl::AimdRateControl()
     : min_configured_bitrate_bps_(
-          RemoteBitrateEstimator::kDefaultMinBitrateBps),
+          remote_bitrate_estimator_defines::kMinBitrateBps),
       max_configured_bitrate_bps_(30000000),
       current_bitrate_bps_(max_configured_bitrate_bps_),
       avg_max_bitrate_kbps_(-1.0f),