Remove closePath()

[manstie]

closePath "attempts to add a straight line from the current point to the start of the current sub-path" so for a straight line it does nothing, and for a curve it draws back to the start point so if you draw quickly you get an ugly two line effect.

[brinley]

Have you done much cross browser testing? especially in older browsers?

[manstie]

It works to specification in IE11

I would assume it appears the same for all browsers listed in the compatibility table here