message: Adopt absl::string_view in modules/audio_mixer/
  Cr-Commit-Position: refs/heads/main@{#37792}
diff: @@ -46,7 +46,7 @@ namespace test {
  class FilePlayingSource : public AudioMixer::Source {
  public:
  - explicit FilePlayingSource(std::string filename)
  + explicit FilePlayingSource(absl::string_view filename)
  : wav_reader_(new WavReader(filename)),
  sample_rate_hz_(wav_reader_->sample_rate()),
  samples_per_channel_(sample_rate_hz_ / 100),
  