toDataURL doesn't respect the zoom level of the canvas, this PR uses the multiplier attribute to ensure the canvas contents are scaled properly.
Steps to reproduce bug: Paste an image, zoom such that the image is much smaller, download or publish the meme and there will be whitespace around the image
Steps to reproduce bug: Paste an image, zoom such that the image is much smaller, download or publish the meme and there will be whitespace around the image