[manifest] What's the use case for theme_color? (#356)

```theme_color``` in the Manifest sounds fairly odd. Discussing with @PaulKinlan and @marcoscaceres, my understanding is that it was meant as a defaul theme_color for the meta tag. However, this is not possible because the UA might want to have a theme_color value for the first paint but Manifest can't block the first paint.

I would understand that it could be used for UI-related features but I would prefer to avoid keeping things in the Manifest "in case of". Is there interest to use theme_color by an implementation?

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/manifest/issues/356