We cannot directly resize the DOM canvas element using typical HTML functionality (for instance the ability to resize a textarea input in a form by dragging its bottom right corner) - the canvas element's bitmap and CSS dimensions are different attributes which do not play nicely together. Thus browsers will ignore any attempt to attach a draggable resize widget to the canvas element (using the CSS 'resize' property).
To overcome this issue we enclose the canvas element in a Scrawl-canvas stack element, add the resize property to that, and set the canvas dimensions to 100% of the Stack's dimensions. Even so, only Firefox seems to allow the canvas element to be resized dynamically using this fix; Chrome, for instance, shows the corner resize dragger as expected, but doesn't respond to user interaction.
Exposing the hidden canvases (cells), for development purposes only: