Assume pending buffered bytes is zero when ALSA has underrun.

media/audio/linux/alsa_wrapper.cc

Index: media/audio/linux/alsa_wrapper.cc
diff --git a/media/audio/linux/alsa_wrapper.cc b/media/audio/linux/alsa_wrapper.cc
index 303a1f1c51b1b39e3cea0e68eabb2c477189fea2..a028484c1f80caf71da4a435becdef184a12f9e2 100644
--- a/media/audio/linux/alsa_wrapper.cc
+++ b/media/audio/linux/alsa_wrapper.cc
@@ -1,4 +1,4 @@
-// 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.
 
@@ -71,6 +71,10 @@ snd_pcm_sframes_t AlsaWrapper::PcmAvailUpdate(snd_pcm_t* handle) {
   return snd_pcm_avail_update(handle);
 }
 
+snd_pcm_state_t AlsaWrapper::PcmState(snd_pcm_t* handle) {
+  return snd_pcm_state(handle);
+}
+
 const char* AlsaWrapper::StrError(int errnum) {
   return snd_strerror(errnum);
 }