Expose `jitterBufferEmittedCount` in addition to the existing `jitterBufferDelay` for `getStats()`.

NetEq currently only passes `jitterBufferDelay` to `getStats()`. We need its paired `jitterBufferEmittedCount` denominator stat for the calculations to be accurate.

Bug: webrtc:10192
Change-Id: I655aea629026ce9101409c2e0f18c2fa57a1c3ab
Reviewed-on: https://webrtc-review.googlesource.com/c/117320
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Chen Xing <chxg@google.com>
Cr-Commit-Position: refs/heads/master@{#26276}
diff --git a/media/base/media_channel.h b/media/base/media_channel.h
index 8eecaa0..a55c191 100644
--- a/media/base/media_channel.h
+++ b/media/base/media_channel.h
@@ -449,7 +449,8 @@
   double total_output_duration = 0.0;
   uint64_t concealed_samples = 0;
   uint64_t concealment_events = 0;
-  double jitter_buffer_delay_seconds = 0;
+  double jitter_buffer_delay_seconds = 0.0;
+  uint64_t jitter_buffer_emitted_count = 0;
   // Stats below DO NOT correspond directly to anything in the WebRTC stats
   // fraction of synthesized audio inserted through expansion.
   float expand_rate = 0.0f;