Implement audio recording for Linux via ALSA.

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 a70856ab59d374d513f069289270a4e8721f94c6..8270430d1946d5d15fe31b286960e9f223058d10 100644
--- a/media/audio/linux/alsa_wrapper.cc
+++ b/media/audio/linux/alsa_wrapper.cc
@@ -51,6 +51,12 @@ snd_pcm_sframes_t AlsaWrapper::PcmWritei(snd_pcm_t* handle,
   return snd_pcm_writei(handle, buffer, size);
 }
 
+snd_pcm_sframes_t AlsaWrapper::PcmReadi(snd_pcm_t* handle,
+                                        void* buffer,
+                                        snd_pcm_uframes_t size) {
+  return snd_pcm_readi(handle, buffer, size);
+}
+
 int AlsaWrapper::PcmRecover(snd_pcm_t* handle, int err, int silent) {
   return snd_pcm_recover(handle, err, silent);
 }
@@ -83,3 +89,8 @@ snd_pcm_state_t AlsaWrapper::PcmState(snd_pcm_t* handle) {
 const char* AlsaWrapper::StrError(int errnum) {
   return snd_strerror(errnum);
 }
+
+int AlsaWrapper::PcmStart(snd_pcm_t* handle) {
+  return snd_pcm_start(handle);
+}
+