message: Optimize portable MatrixScalarMultiply method.
diff: @@ -281,9 +281,11 @@ void PortableMatrixScalarMultiplyAccumulate(const int8_t* matrix,
  int32_t scalar, int32_t n_row,
  int32_t n_col, int32_t* output) {
  for (int i = 0; i < n_row; ++i) {
  + int32_t row_sum = 0;
  for (int j = 0; j < n_col; ++j) {
  - output[i] += matrix[i * n_col + j] * scalar;
  + row_sum += *matrix++;
  }
  + output[i] += row_sum * scalar;
  }
  }
  