Make access of window.devicePixelRatio safer
Make access of window.devicePixelRatio safer

Not sure if it’ll be undefined on browsers that also have <canvas> but
I don’t think this’ll hurt anything.

vilterp/core,Pisys/core,manleyjster/core,krisajenkins/core,rgrempel/core,bradurani/core,isaacsanders/core,krisajenkins/core,suryagaddipati/core,ThomasWeiser/core,vilterp/core,alexiamcdonald/elm-core,ThomasWeiser/core,bradurani/core,rgrempel/core,rick68/core,martinos/core,simonh1000/core,manleyjster/core,rick68/core,Dandandan/core,eeue56/core,simonh1000/core,colinmccabe/core,alexiamcdonald/elm-core,eeue56/core,martinos/core,Dandandan/core,laszlopandy/core,isaacsanders/core,laszlopandy/core,colinmccabe/core,suryagaddipati/core,Pisys/core