Unittests for loss based bandwidth estimation.

Bug: none
Change-Id: I204071683c1c6e28040ea3bce900c4b04108cba7
Reviewed-on: https://webrtc-review.googlesource.com/c/112380
Commit-Queue: Christoffer Rodbro <crodbro@webrtc.org>
Reviewed-by: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25844}
diff --git a/modules/bitrate_controller/loss_based_bandwidth_estimation.cc b/modules/bitrate_controller/loss_based_bandwidth_estimation.cc
index 5d7f8aa..f22f970 100644
--- a/modules/bitrate_controller/loss_based_bandwidth_estimation.cc
+++ b/modules/bitrate_controller/loss_based_bandwidth_estimation.cc
@@ -156,9 +156,9 @@
   if (acknowledged_bitrate > acknowledged_bitrate_max_) {
     acknowledged_bitrate_max_ = acknowledged_bitrate;
   } else {
-    acknowledged_bitrate_max_ +=
+    acknowledged_bitrate_max_ -=
         ExponentialUpdate(config_.acknowledged_rate_max_window, time_passed) *
-        (acknowledged_bitrate - acknowledged_bitrate_max_);
+        (acknowledged_bitrate_max_ - acknowledged_bitrate);
   }
 }