The following document mentions some guidelines for performant scaling of HTML5 Canvas: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Optimizing_canvas#Scaling_canvas_using_CSS_transforms
CSS transforms are faster by using the GPU. Best case is to not scale the canvas or have a smaller canvas and scale up rather than a bigger canvas and scale down. For Firefox OS, target 480 x 320 px.
This is unclear. Should I make the canvas as small as possible, then scale with CSS, or set the larger canvas dimensions from the canvas.width and canvas.height attributes (and "not scale the canvas" at all?)