Add stats totalSamplesReceived and concealedSamples

Adds two new stats to RTCMediaStreamTrackStats:
* totalSamplesReceived is the total number of samples received on
      the audio channel and includes real and synthetic samples.
* concealedSamples is the total number of synthetic samples
      received on the audio channel used to conceal packet loss.

Bug: webrtc:8076
Change-Id: I36e9828525ec341490cf3310a972b56a8b443667
Reviewed-on: https://chromium-review.googlesource.com/615902
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19506}

webrtc/modules/audio_coding/neteq/include/neteq.h

@@ -58,6 +58,18 @@ struct NetEqNetworkStatistics {
   int max_waiting_time_ms;
 };
 
+// NetEq statistics that persist over the lifetime of the class.
+// These metrics are never reset.
+struct NetEqLifetimeStatistics {
+  // Total number of audio samples received, including synthesized samples.
+  // https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamtrackstats-totalsamplesreceived
+  uint64_t total_samples_received = 0;
+  // Total number of inbound audio samples that are based on synthesized data to
+  // conceal packet loss.
+  // https://w3c.github.io/webrtc-stats/#dom-rtcmediastreamtrackstats-concealedsamples
+  uint64_t concealed_samples = 0;
+};
+
 enum NetEqPlayoutMode {
   kPlayoutOn,
   kPlayoutOff,
@@ -220,6 +232,10 @@ class NetEq {
   // after the call.
   virtual int NetworkStatistics(NetEqNetworkStatistics* stats) = 0;
 
+  // Returns a copy of this class's lifetime statistics. These statistics are
+  // never reset.
+  virtual NetEqLifetimeStatistics GetLifetimeStatistics() const = 0;
+
   // Writes the current RTCP statistics to |stats|. The statistics are reset
   // and a new report period is started with the call.
   virtual void GetRtcpStatistics(RtcpStatistics* stats) = 0;