Forward the number of skipped frames by the OS in audio playout.

media/audio/mac/audio_auhal_mac.h

Index: media/audio/mac/audio_auhal_mac.h
diff --git a/media/audio/mac/audio_auhal_mac.h b/media/audio/mac/audio_auhal_mac.h
index 0cd648a90253fada50c3d6ee073defdca8f3967a..bd830d32946f81687caa95933632479cd8b58632 100644
--- a/media/audio/mac/audio_auhal_mac.h
+++ b/media/audio/mac/audio_auhal_mac.h
@@ -126,7 +126,9 @@ class AUHALStream : public AudioOutputStream {
   // Gets the current playout latency value.
   double GetPlayoutLatency(const AudioTimeStamp* output_time_stamp);
 
-  void UpdatePlayoutTimestamp(const AudioTimeStamp* timestamp);
+  // Updates playout timestamp, current lost frames, and total lost frames and
+  // glitches stats.
+  void UpdatePlayoutTimestampAndStats(const AudioTimeStamp* timestamp);
 
   // Called from the dtor and when the stream is reset.
   void ReportAndResetStats();
@@ -182,6 +184,11 @@ class AUHALStream : public AudioOutputStream {
   // Current buffer delay.  Set by Render().
   uint32 current_hardware_pending_bytes_;
 
+  // Lost frames not yet reported to the provider. Increased in
+  // UpdatePlayoutTimestampAndStats() if any lost frame since last time.
+  // Forwarded to the provider and reset in ProvideInput().
+  uint32_t current_lost_frames_;
+
   // Stores the timestamp of the previous audio buffer requested by the OS.
   // We use this in combination with |last_number_of_frames_| to detect when
   // the OS has decided to skip rendering frames (i.e. a glitch).