A canvas which ignores all drawing commands.

	private
	apply: clipBy:during: transformBy:clippingTo:during:smoothing: translateBy:during:

	canvas methods	top
	clipRect Return the currently active clipping rectangle
	copyClipRect: who cares what the clipping rectangle is?
	extent Return the physical extent of the output device
	form
	isBalloonCanvas
	isShadowDrawing
	origin Return the current origin for drawing operations

	private	top
	apply: do nothing
	clipBy:during: do this in order that timing runs work better
	transformBy:clippingTo:during:smoothing: do this in order that timing runs work better
	translateBy:during: do this in order that timing runs work better