Don't assume fill for canvas polygon hit detection.
Don't assume fill for canvas polygon hit detection.

This brings canvas polygon hit detection in parity with WebGL, where an
unfilled polygon will not be hit detected hovering inside the polygon.

Fixes #4846

ahocevar/ol3,stweil/openlayers,bjornharrtell/ol3,adube/ol3,ahocevar/openlayers,ahocevar/ol3,openlayers/openlayers,ahocevar/ol3,geekdenz/openlayers,geekdenz/ol3,bjornharrtell/ol3,bjornharrtell/ol3,ahocevar/openlayers,mzur/ol3,fredj/ol3,stweil/ol3,ahocevar/ol3,mzur/ol3,stweil/ol3,fredj/ol3,stweil/ol3,geekdenz/ol3,oterral/ol3,stweil/openlayers,tschaub/ol3,ahocevar/openlayers,mzur/ol3,adube/ol3,geekdenz/openlayers,stweil/openlayers,tschaub/ol3,stweil/ol3,geekdenz/ol3,oterral/ol3,oterral/ol3,mzur/ol3,geekdenz/openlayers,adube/ol3,openlayers/openlayers,tschaub/ol3,openlayers/openlayers,tschaub/ol3,geekdenz/ol3,fredj/ol3,fredj/ol3