Man, what are you asking about !!! visiting Iran is not a crime !!!!!!
Dispite the bad relation between the 2 countries, Iranian people are allowed to immigrate to canada .
If they are going to refuse your application Just because you have visited Iran, they would not have allowed Iranian People to immigrate to canada at all, furthermore, giving them recently more facilities regarding the immigration procedures.
As long as you mentioned in your application the number of countries that you have visited by giving police clearance from each country, you are fine and have no problems at all.
Have a look at this link:
http://www.cic.gc.ca/english/resources/manuals/bulletins/2009/ob148.asp