The setSubpixelCSSOMElementMetricsEnabled pref was a failed experiment; we should remove all the prefs and related code.
I only find reference to this on Webkit Github here: https://github.com/WebKit/WebKit/blob/7c2a4a43c12f7f5694e5de385d4c4ec713afe56f/Source/WebKitLegacy/mac/WebView/WebPreferences.mm#L3278 Is it remove these lines? Thanks! Rest of this was I think removed here - https://github.com/WebKit/WebKit/commit/d9c3d4261b55a19fe34d3134b2d4f229bc40701d Is something needed here? Thanks!
This code has since been removed.