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

media/audio/mac/audio_auhal_mac.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Implementation notes:
 //
 // - It is recommended to first acquire the native sample rate of the default
 //   output device and then use the same rate when creating this object.
 //   Use AudioManagerMac::HardwareSampleRate() to retrieve the sample rate.
 // - Calling Close() also leads to self destruction.
@@ skipping 108 matching lines @@
   // Creates the input and output busses.
   void CreateIOBusses();
 
   // Gets the fixed playout device hardware latency and stores it. Returns 0
   // if not available.
   double GetHardwareLatency();
 
   // Gets the current playout latency value.
   double GetPlayoutLatency(const AudioTimeStamp* output_time_stamp);
 
+  // Updates playout timestamp, current lost frames, and total lost frames and
+  // glitches.
   void UpdatePlayoutTimestamp(const AudioTimeStamp* timestamp);
 
   // Called from the dtor and when the stream is reset.
   void ReportAndResetStats();
 
   // Our creator, the audio manager needs to be notified when we close.
   AudioManagerMac* const manager_;
 
   const AudioParameters params_;
   // For convenience - same as in params_.
@@ skipping 36 matching lines @@
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> output_bus_;
 
   // Dynamically allocated FIFO used when CoreAudio asks for unexpected frame
   // sizes.
   scoped_ptr<AudioPullFifo> audio_fifo_;
 
   // Current buffer delay.  Set by Render().
   uint32 current_hardware_pending_bytes_;
 
+  // Lost frames not yet reported to the provider. Increased in
+  // UpdatePlayoutTimestamp() 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).
   // This can happen in case of high CPU load or excessive blocking on the
   // callback audio thread.
   // These variables are only touched on the callback thread and then read
   // in the dtor (when no longer receiving callbacks).
   // NOTE: Float64 and UInt32 types are used for native API compatibility.
   Float64 last_sample_time_;
   UInt32 last_number_of_frames_;
   UInt32 total_lost_frames_;
   UInt32 largest_glitch_frames_;
   int glitches_detected_;
 
   // Used to defer Start() to workaround http://crbug.com/160920.
   base::CancelableClosure deferred_start_cb_;
 
   // Used to make sure control functions (Start(), Stop() etc) are called on the
   // right thread.
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(AUHALStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_MAC_AUDIO_AUHAL_MAC_H_