polyfill-service/polyfills/HTMLCanvasElement/prototype/toBlob/polyfill.js

A polyfill combinator

(function () {
	'use strict';

	Object.defineProperty(HTMLCanvasElement.prototype, 'toBlob', {
		value: function (callback, type, quality) {
			var binStr = atob( this.toDataURL(type, quality).split(',')[1] ),
				len = binStr.length,
				arr = new Uint8Array(len);
			for (var i=0; i<len; i++ ) {
				arr[i] = binStr.charCodeAt(i);
			}
			callback(new Blob([arr], { type: type || 'image/png' } ) );
		}
	});
}());