Toronto Mayor Olivia Chow is speaking out about online “trolls” who have been targeting her with “personal vicious attacks.” In a new video posted to her social media accounts, Chow reads and responds to some of the more egregious comments directed at her. A familiar one, she says, is “Go back to China.” “I’ve heard that a few times, by the way, I came from Hong Kong, but are you serious? What kind of racist crap is this?” Her accent is also a f…