Brightness filter not implemented according to spec in Chrome?

dabblet.css

/**
 * Brightness filter not implemented according to spec in Chrome?
 * https://www.w3.org/TR/filter-effects-1/#brightnessEquivalent
 * Red is correct, white is wrong.
 */

div {
	width: 90vmin;
	height: 90vmin;
	background: rgb(25, 0, 0);
	filter: brightness(100000%);
}

dabblet.html

<div></div>

dabblet.js

// alert('Hello world!');

settings.json

{"view":"split-vertical","fontsize":"100","seethrough":"","prefixfree":"","page":"css"}