Introduce AudioBufferMemoryPool to avoid thrashing on audio buffers.

chromecast/media/cma/backend/alsa/audio_decoder_alsa.h

Index: chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
diff --git a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
index 9d72e67731e6f9d16d643ffcdf5ba186d468b53c..c5560b6b85583bc8c6f918674b1e071b0346fc8e 100644
--- a/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
+++ b/chromecast/media/cma/backend/alsa/audio_decoder_alsa.h
@@ -15,6 +15,7 @@
 #include "chromecast/public/media/decoder_config.h"
 #include "chromecast/public/media/media_pipeline_backend.h"
 #include "chromecast/public/media/media_pipeline_device_params.h"
+#include "media/base/audio_buffer.h"
 
 namespace base {
 class SingleThreadTaskRunner;
@@ -110,6 +111,8 @@ class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
   int64_t pending_output_frames_;
   float volume_multiplier_;
 
+  scoped_refptr<::media::AudioBufferMemoryPool> pool_;
+
   base::WeakPtrFactory<AudioDecoderAlsa> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDecoderAlsa);