message: better error msg for incorrect WAV format chunk
diff: @@ -235,7 +235,7 @@ Status DecodeLin16WaveAsFloatVector(const string& wav_string,
  ReadValue<uint32>(wav_string, &format_chunk_size, &offset));
  if ((format_chunk_size != 16) && (format_chunk_size != 18)) {
  return errors::InvalidArgument(
  - "Bad file size for WAV: Expected 16 or 18, but got", format_chunk_size);
  + "Bad format chunk size for WAV: Expected 16 or 18, but got", format_chunk_size);
  }
  uint16 audio_format;
  TF_RETURN_IF_ERROR(ReadValue<uint16>(wav_string, &audio_format, &offset));
  