Flush buffers when stopping audio receive stream.

Bug: chromium:1400642
Change-Id: I19f22ca2fcf04d5e973d0e49fda841c9d40b12a1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/290723
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Jakob Ivarsson‎ <jakobi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#39045}
diff --git a/audio/channel_receive.cc b/audio/channel_receive.cc
index 363eebf..0562d66 100644
--- a/audio/channel_receive.cc
+++ b/audio/channel_receive.cc
@@ -621,6 +621,7 @@
   RTC_DCHECK_RUN_ON(&worker_thread_checker_);
   playing_ = false;
   _outputAudioLevel.ResetLevelFullRange();
+  acm_receiver_.FlushBuffers();
 }
 
 absl::optional<std::pair<int, SdpAudioFormat>> ChannelReceive::GetReceiveCodec()