Reconsider Web App Manifest "theme_color" requirement

Fallow the spec and recognize Web App Manifest theme_color parameter. Currently showing error

Is related to https://github.com/GoogleChrome/lighthouse/pull/2466.

Spec https://w3c.github.io/manifest/#theme_color-member Landed in Chrome 46 https://developers.google.com/web/updates/2015/08/using-manifest-to-set-sitewide-theme-color

https://www.chromestatus.com/feature/5709006190411776 It should be noted that if a theme color is specified as a meta-tag for a certain page (see https://developers.google.com/web/updates/2014/11/Support-for-theme-color-in-Chrome-39-for-Android?hl=en), then the information from the meta tag will override the global theme color option in the manifest for that page.

[laukstein]

FYI, Chrome canary (https://bugs.chromium.org/p/chromium/issues/detail?id=578122) supports now prefers-color-scheme in SVG also used in App Manifest:

<!-- https://blog.tomayac.com/2019/09/21/prefers-color-scheme-in-svg-favicons-for-dark-mode-icons/ -->
<svg width="100" height="100" xmlns="http://www.w3.org/2000/svg">
  <style>
    circle {
      fill: yellow;
      stroke: black;
      stroke-width: 3px;
    }
    @media (prefers-color-scheme: dark) {
      circle {
        fill: black;
        stroke: yellow;
      }
    }
  </style>
  <circle cx="50" cy="50" r="47"/>
</svg>

Would result in light mode:

and in dark mode:

Tested on desktop.

[patrickhulce]

These are all good points. I’m inclined to reduce the requirement to specifies theme-color, warn if theme_color is not set and just documenting why we suggest setting both.

Does anyone else on LH disagree?