Round canvas.style dimensions to avoid blurring (#9015)

When canvas.height and canvas.width are set, the numbers are rounded to
integers. The same rounding must be applied to canvas.style.height and
canvas.style.width to avoid scaling of the canvas which would lead to
blurring.

Acknowledging that canvas.height and canvas.width are integers, the
framebuffer is now only redrawn if those integer values change.