Add UMA stats for OS input glitches on Mac.

media/audio/mac/audio_auhal_mac.cc

 // 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.
 
 #include "media/audio/mac/audio_auhal_mac.h"
 
 #include <CoreServices/CoreServices.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 195 matching lines @@
     AudioBufferList* data) {
   TRACE_EVENT0("audio", "AUHALStream::Render");
 
   UpdatePlayoutTimestamp(output_time_stamp);
 
   // If the stream parameters change for any reason, we need to insert a FIFO
   // since the OnMoreData() pipeline can't handle frame size changes.
   if (number_of_frames != number_of_frames_) {
     // Create a FIFO on the fly to handle any discrepancies in callback rates.
     if (!audio_fifo_) {
+      // TODO(grunell): We'll only care about the first buffer size change,
+      // any further changes will be ignored. It would be nice to have all
+      // changes reflected in UMA stats.
       number_of_frames_requested_ = number_of_frames;
       DVLOG(1) << "Audio frame size changed from " << number_of_frames_
                << " to " << number_of_frames
                << "; adding FIFO to compensate.";
       audio_fifo_.reset(new AudioPullFifo(
           output_channels_,
           number_of_frames_,
           base::Bind(&AUHALStream::ProvideInput, base::Unretained(this))));
     }
   }
@@ skipping 317 matching lines @@
   OSStatus result = AudioUnitUninitialize(audio_unit_);
   OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
       << "AudioUnitUninitialize() failed.";
   result = AudioComponentInstanceDispose(audio_unit_);
   OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
       << "AudioComponentInstanceDispose() failed.";
   audio_unit_ = 0;
 }
 
 }  // namespace media