Adiel said it perfectly for this project... but I would add for general knowledge ( from long years of using this stuff ) that one might want to test any foam which it was going to be used with in a small spot first.... it dissolves some.... but not the kind usually used with cars.... and that when planning a glue up try to choose parts which are going to go Straight onto each other... there is no provision for aligning this after they have been placed together... Looking at the picture you posted... and since contact cement is very strong... you might get a way with only using an inch by a half inch along the area where the vinyl meets vinyl along the edge... In other words you do not need to coat all the back of the mirror holder and the place it is going in order to hold it just fine...

Jeff, weatherstrip adhesive is contact cement...