Assume pending buffered bytes is zero when ALSA has underrun.

media/audio/linux/alsa_wrapper.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 //
 // AlsaWrapper is a simple stateless class that wraps the alsa library commands
 // we want to use.  It's purpose is to allow injection of a mock so that the
 // higher level code is testable.
 
 #include <alsa/asoundlib.h>
 
 #include "base/basictypes.h"
@@ skipping 16 matching lines @@
   virtual snd_pcm_sframes_t PcmWritei(snd_pcm_t* handle,
                                       const void* buffer,
                                       snd_pcm_uframes_t size);
   virtual int PcmRecover(snd_pcm_t* handle, int err, int silent);
   virtual int PcmSetParams(snd_pcm_t* handle, snd_pcm_format_t format,
                            snd_pcm_access_t access, unsigned int channels,
                            unsigned int rate, int soft_resample,
                            unsigned int latency);
   virtual const char* PcmName(snd_pcm_t* handle);
   virtual snd_pcm_sframes_t PcmAvailUpdate(snd_pcm_t* handle);
+  virtual snd_pcm_state_t PcmState(snd_pcm_t* handle);
 
   virtual const char* StrError(int errnum);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AlsaWrapper);
 };