[whatwg] getImageData/putImageData comments

[Boris Zbarsky]

Ian Hickson wrote:
> I don't see why the imagedata API isn't suitable for that. It's not like 
> if you're painting that on the canvas you'll want to leave the last row or 
> column unaffected. You'll want to clear it or some such, in practice.

I believe in this case the page actually wants to create a canvas for 
each intermediate state, so needs to create canvases sized 1 imagedata 
pixel smaller than a given canvas....  Just painting to a canvas of the 
old size isn't right, since it'll then take too much space in the layout.

-Boris