For example expose something like the HACK_FORCE_TEXT_AUTOSIZING_ON_DESKTOP from Settings.cpp in Chromium's about:flags. Is there a more universal way of doing something like this (it would be nice if all ports implemented some kind of about:webkit-flags...)?
Marking this bug Resolved WontFix because the TEXT_AUTOSIZING feature was removed in <https://trac.webkit.org/changeset/206119> (bug #162167). See bug 84186, comment 32 for more details.