I'd say the pot's simmering, rather than boiling. The Japanese are certainly not pushovers, but of course from the standpoint of Chinese domestic politics standing up to the Japanese carries a lot of flag-waving nationalist points that the Chinese government will be eager to score. They will not want that to boil, though, let alone boil over, so I'd expect them to keep just enough heat on to generate a simmer without ever pushing too near the boiling point.