8eaa2cbce3
According to [MDN](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/setLineDash#Browser_compatibility) the standard versions of these methods have been supported since Firefox 27, which was released over two and a half years ago. (See the dates in https://wiki.mozilla.org/RapidRelease/Calendar#Past_branch_dates) Furthermore the non-standard properties are now in the process of being removed, please see https://groups.google.com/forum/#!topic/mozilla.dev.platform/UIudMABegcY. Hence I don't think that we need to keep the old `moz` prefixed ones as fallback any more.