China is getting very long-term leases on large swaths of territory in the Far East. There is officially no exterritoriality, yet with increasing number of Chinese people there while Russian population there is minuscule (and even that is mostly not ethnically Russians, instead it is the local ethnicities whose history with China is much longer than with Russia), remoteness of Moscow and Russian bureaucrats' total corruption - there is no need for the official declaration. So, while today China still can't ask for Vladivostok and other "historically Chinese territories" (according to the modern Chinese official maps), tomorrow they wouldn't even have to.