Similar to to bug 210695. WebKit stores the env variable values in the inherited properties.
Created attachment 396880 [details] Patch
Created attachment 396906 [details] Patch for landing
Annti Koivisto found in /Volumes/Data/worker/Commit-Queue/build/LayoutTests/ChangeLog does not appear to be a valid reviewer according to contributors.json. /Volumes/Data/worker/Commit-Queue/build/LayoutTests/ChangeLog neither lists a valid reviewer nor contains the string "Unreviewed" or "Rubber stamp" (case insensitive).
Whoops, that happens for filing the changelog manually :)
Created attachment 396907 [details] Patch for landing
Found 1 new test failure: fast/layoutformattingcontext/simple-absolute-positioned-replaced-inline-element-with-percentage-height.html
Comment on attachment 396907 [details] Patch for landing Doesn't look related.
Committed r260340: <https://trac.webkit.org/changeset/260340> All reviewed patches have been landed. Closing bug and clearing flags on attachment 396907 [details].