Fix bug in how send timestamps are converted to 24 bits.

webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc

Index: webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
index 56a309c59db9174454f0ef4750ba03fff0e31747..522489e921347ec4b25485452e834a43804fd30c 100644
--- a/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
+++ b/webrtc/modules/remote_bitrate_estimator/remote_bitrate_estimator_abs_send_time.cc
@@ -64,6 +64,15 @@ std::vector<K> Keys(const std::map<K, V>& map) {
   return keys;
 }
 
+uint32_t ConvertMsTo24Bits(int64_t time_ms) {
+  uint32_t time_24_bits =
+      static_cast<uint32_t>(
+          ((static_cast<uint64_t>(time_ms) << kAbsSendTimeFraction) + 500) /
+          1000) &
+      0x00FFFFFF;
+  return time_24_bits;
+}
+
 bool RemoteBitrateEstimatorAbsSendTime::IsWithinClusterBounds(
     int send_delta_ms,
     const Cluster& cluster_aggregate) {
@@ -219,12 +228,8 @@ bool RemoteBitrateEstimatorAbsSendTime::IsBitrateImproving(
 void RemoteBitrateEstimatorAbsSendTime::IncomingPacketFeedbackVector(
     const std::vector<PacketInfo>& packet_feedback_vector) {
   for (const auto& packet_info : packet_feedback_vector) {
-    // TODO(holmer): We should get rid of this conversion if possible as we may
-    // lose precision.
-    uint32_t send_time_32bits = (packet_info.send_time_ms) / kTimestampToMs;
-    uint32_t send_time_24bits =
-        send_time_32bits >> kAbsSendTimeInterArrivalUpshift;
-    IncomingPacketInfo(packet_info.arrival_time_ms, send_time_24bits,
+    IncomingPacketInfo(packet_info.arrival_time_ms,
+                       ConvertMsTo24Bits(packet_info.send_time_ms),
                        packet_info.payload_size, 0, packet_info.was_paced);
   }
 }