Re: [csswg-drafts] [css-color-4] Some example HWB-to-RGB translations are incorrect (#5531)

> It may be worth solving this issue for implementers who copy the hwbToRgb() function by including the whiteness/blackness normalization logic in the function itself:

Agreed. Currently the spec handwaves here: [The following Javascript implementation of the algorithm assumes that the white and black components have already been normalized, so their sum is no larger than 100%, and have been converted into numbers in the range [0,1].](https://drafts.csswg.org/css-color-4/#hwb-to-rgb)

I tend to agree that it is better to do the normalization in the sample code.

Here is what [color.js does](https://github.com/LeaVerou/color.js/blob/master/src/spaces/hwb.js):

```js
from: {
		srgb (rgb) {
			let h = Color.spaces.hsl.from.srgb(rgb)[0];
			// calculate white and black
			let w = Math.min(...rgb);
			let b = 1 - Math.max(...rgb);
			w *= 100;
			b *= 100;
			return [h, w, b];
		},

		hsv (hsv) {
			let [h, s, v] = hsv;

			return [h, v * (100 - s) / 100, 100 - v];
		}
	},
```

and

```js
to: {
		srgb (hwb) {
			let [h, w, b] = hwb;

			// Now convert percentages to [0..1]
			w /=100;
			b /= 100;

			// Normalize so white plus black is no larger than 100
			let sum = w + b;
			if (sum > 1) {
				 w /= sum;
				 b /= sum;
			}

			// From https://drafts.csswg.org/css-color-4/#hwb-to-rgb
			let rgb = Color.spaces.hsl.to.srgb([h, 100, 50]);
			for (var i = 0; i < 3; i++) {
				rgb[i] *= (1 - w - b);
				rgb[i] += w;
			}
			return rgb;
		}
	},
```

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