HONG KONG — Hundreds of pro-democracy protesters turned their backs on the Chinese flag Wednesday morning as it was flown over Hong Kong’s Victoria Harbor in celebration of the country’s National Day holiday. Tens of thousands of others continued their blockade of key roads in the city’s business and commercial districts. On the fourth day of protests, demonstrators showed no sign of giving up. Many had spent the night sleeping through a thunderstorm on wet concrete. This all comes as a shock to some of the mainland Chinese residents who arrived in the city today at the start of their seven-day holiday, known as “Golden Week” — traditionally a time for travel and shopping.