I have found this on CIC website:
"As part of a complete application, applicants, their spouse or common-law partner and their dependent children 18 years of age or older (including non-accompanying dependents) must submit a valid police certificate for all countries or territories (except Canada) in which they have lived for a total of six months or more, since the age of 18."
and
"The Canadian visa office will tell you if you need a Canadian criminal record check while your application is being processed."
So I believe I don`t need to provide them with a police certificate right now; they`ll ask me for one if needed