NetEq: Fix stats counting in muted mode

The NetEqNetworkStatistics::expand_rate was not incremented during muted
state, which caused under-reporting of that metric. This change fixes
that.

BUG=chromium:613321, webrtc:5608

Review-Url: https://codereview.webrtc.org/2003203004
Cr-Commit-Position: refs/heads/master@{#12894}
diff --git a/webrtc/modules/audio_coding/neteq/neteq_impl.cc b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
index 7aeeb73..87d12f5 100644
--- a/webrtc/modules/audio_coding/neteq/neteq_impl.cc
+++ b/webrtc/modules/audio_coding/neteq/neteq_impl.cc
@@ -832,6 +832,7 @@
             : timestamp_scaler_->ToExternal(playout_timestamp_) -
                   static_cast<uint32_t>(audio_frame->samples_per_channel_);
     audio_frame->num_channels_ = sync_buffer_->Channels();
+    stats_.ExpandedNoiseSamples(output_size_samples_);
     *muted = true;
     return 0;
   }