The serialization of scroll-offsets in the spec should be updated: https://github.com/w3c/csswg-drafts/issues/6617 Besides, some other updates should also be addressed in Chromium: 1. start/end should be replaced by scroll-offsets: * Chromium issue: https://bugs.chromium.org/p/chromium/issues/detail?id=1074059 2. time-range should be removed: * Chromium issue: https://bugs.chromium.org/p/chromium/issues/detail?id=1216655 Differential Revision: https://phabricator.services.mozilla.com/D125767