Reland of "Reporting of decoding_codec_plc events""

This is a reland of 0a88ea050cda58de81d624cf2764d46929447ed5.

The new stat will not be reported unless it is GT 0.

Reporting of decoding_codec_plc events

Bug: webrtc:10838
Change-Id: Ic8585b4eeae9a2643374f15bc2578d1141e59683
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/148448
Reviewed-by: Magnus Flodman <mflodman@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Alex Narest <alexnarest@google.com>
Cr-Commit-Position: refs/heads/master@{#28797}

modules/audio_coding/neteq/neteq_impl.h

@@ -64,7 +64,14 @@ struct PreemptiveExpandFactory;
 
 class NetEqImpl : public webrtc::NetEq {
  public:
-  enum class OutputType { kNormalSpeech, kPLC, kCNG, kPLCCNG, kVadPassive };
+  enum class OutputType {
+    kNormalSpeech,
+    kPLC,
+    kCNG,
+    kPLCCNG,
+    kVadPassive,
+    kCodecPLC
+  };
 
   enum ErrorCodes {
     kNoError = 0,