Make OS audio buffer size limits visible.

media/audio/cras/audio_manager_cras.cc

Index: media/audio/cras/audio_manager_cras.cc
diff --git a/media/audio/cras/audio_manager_cras.cc b/media/audio/cras/audio_manager_cras.cc
index 2e6d346e73bb1d47d5c343911e4bcb6417d079ac..7ff09902989c9d53c130c17fab2bdc5f5a0bd062 100644
--- a/media/audio/cras/audio_manager_cras.cc
+++ b/media/audio/cras/audio_manager_cras.cc
@@ -369,4 +369,12 @@ bool AudioManagerCras::IsDefault(const std::string& device_id, bool is_input) {
   return device_name.unique_id == device_id;
 }
 
+int AudioManager::GetMinimumAudioBufferSize(int sample_rate) {
+  return GetMinimumOutputBufferSizePerBoard();
+}
+
+int AudioManager::GetMaximumAudioBufferSize(int sample_rate) {
+  return kMaximumOutputBufferSize;
+}
+
 }  // namespace media