In the current code, when favicons are found for a page, they are cached for the page's URL and the server-side redirect chain that led to that page.
For client-side redirects, no equivalent exists, except a workaround that strips the fragment/ref of the URL.
Ideally, anything that is perceived as a redirect by the user (e.g. meta refresh tag, Javascript location overrides, history API) should be treated similarly to server-side redirects for favicon purposes. Not doing so results in NTP tiles without icons (or with less icons).
(Desktop thumbnails might be affected by the same issue)
Known examples of gray (or colored) NTP tiles include:
www.hrs.de (redirects to touch.hrs.de)
maps.google.com (redirects to e.g. https://www.google.com/maps/@48.142803,11.5411858,17z)
mail.google.com (a series of server-side redirects followed by client-side ones)
Comment 1 by bugdroid1@chromium.org
, Jul 13 2017