All `WI.Setting` keys are prefixed with `com.apple.WebInspector`, followed by the inspection level, and finally the name of the setting. `WI.Setting.migrateValue` doesn't take that into account, meaning that it doesn't actually read the key it's supposed to be taking the value from.
Created attachment 360082 [details] Patch
Comment on attachment 360082 [details] Patch r=me
Comment on attachment 360082 [details] Patch Clearing flags on attachment: 360082 Committed r240487: <https://trac.webkit.org/changeset/240487>
All reviewed patches have been landed. Closing bug.
<rdar://problem/47556137>