Add more NetEq information to NetEqState.

Some important NetEq information was not available in NetEqState, which
meant it was not available on the API. This CL adds additional
information.

Bug: webrtc:9667
Change-Id: I702707c7d60472f488047d48fb286f839c5608dc
Reviewed-on: https://webrtc-review.googlesource.com/c/102300
Reviewed-by: Minyue Li <minyue@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Ivo Creusen <ivoc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#24985}

modules/audio_coding/neteq/statistics_calculator.h

@@ -83,6 +83,9 @@ class StatisticsCalculator {
   // Reports that |num_samples| samples were decoded from secondary packets.
   void SecondaryDecodedSamples(int num_samples);
 
+  // Rerport that the packet buffer was flushed.
+  void FlushedPacketBuffer();
+
   // Logs a delayed packet outage event of |outage_duration_ms|. A delayed
   // packet outage event is defined as an expand period caused not by an actual
   // packet loss, but by a delayed packet.