[ews] Add unit test to prevent multiple schedulers for a builder. This unit-test would catch potential issues where a builder is mistakenly added to multiple schedulers, e.g.: https://bugs.webkit.org/show_bug.cgi?id=208860#c9
Created attachment 393237 [details] Patch
Comment on attachment 393237 [details] Patch r=me nice! thanks :)
Committed r258261: <https://trac.webkit.org/changeset/258261> All reviewed patches have been landed. Closing bug and clearing flags on attachment 393237 [details].
<rdar://problem/60322627>