For decades Hong Kong was a British piece of territory that had been obtained via force from the Chinese government. It was captured by the Japanese during World War II and when Communist forces swept through the land they halted at the outskirts of the British held city. It was simply a matter of time before the English left the area, but they did receive assurances from the Communist government that Hong Kong would have special status and its people could still retain the right to vote.
Of course, when Chinese Communists promise the right to vote, they mean for their people. The people of Hong Kong do vote but power remains in the hands of officials selected by the Communist government. Its current chief executive, Leung Chun-ying has aroused anger by secretly building on his property in violation of the law as well as his policy of doing what they want in Beijing. There are demonstrations, riots and protests, but the chief executive complains they only represent a few.
Hopefully, it is a matter of time before the Communist government alters its totalitarian status and allows Chinese people their right to truly a free election.