[manifest] Manifest "sizes" fallback logic (#409)

Reference: https://lists.w3.org/Archives/Public/public-webapps/2015OctDec/0064.html

Does "[sizes](https://w3c.github.io/manifest/#sizes-member)" has any fallback for device required different icon sizes?

    {
        "icons": [
            {
                "src": "32x32.png",
                "sizes": "32x32"
            }, {
                "src": "48x48.png",
                "sizes": "48x48"
            }, {
                "src": "128x128.png",
                "sizes": "128x128"
            }
        ]
    }

1. For example, would device request for 16x16 return scaled down image 32x32.png?
2. What about request 40x40 - would it scale up 32x32.png or scale down 48x48.png (40x40 is in middle of both those sizes (+8 = 48, -8 = 32))?
3. Would request 96x96 use 128x128.png?
4. Would request 192x192 and 512x512 use 128x128.png?

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/issues/409