NetEq: Fix a bug in expand_rate and speech_expand_rate calculation

webrtc/modules/audio_coding/neteq/neteq_impl.cc

Index: webrtc/modules/audio_coding/neteq/neteq_impl.cc
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.cc b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
index e119d9439cfbb617f38dfe27c1a9773792f8664c..2d91b8c1c548204d8f78168cc5727feca6b23606 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.cc
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
@@ -1600,16 +1600,18 @@ void NetEqImpl::DoMerge(int16_t* decoded_buffer, size_t decoded_length,
   size_t new_length = merge_->Process(decoded_buffer, decoded_length,
                                       mute_factor_array_.get(),
                                       algorithm_buffer_.get());
-  size_t expand_length_correction = new_length -
-      decoded_length / algorithm_buffer_->Channels();
+  // Correction can be negative.
+  int expand_length_correction =
+      rtc::dchecked_cast<int>(new_length) -
+      rtc::dchecked_cast<int>(decoded_length / algorithm_buffer_->Channels());
 
   // Update in-call and post-call statistics.
   if (expand_->MuteFactor(0) == 0) {
     // Expand generates only noise.
-    stats_.ExpandedNoiseSamples(expand_length_correction);
+    stats_.ExpandedNoiseSamplesCorrection(expand_length_correction);
   } else {
     // Expansion generates more than only noise.
-    stats_.ExpandedVoiceSamples(expand_length_correction);
+    stats_.ExpandedVoiceSamplesCorrection(expand_length_correction);
   }
 
   last_mode_ = kModeMerge;