Fix Flow error in tsrc/
Fix Flow error in tsrc/

Summary:
{D4269082} taught Flow about `Set.constructor`, which helped Flow see
an error in tsrc/. This fixes that error.

Wish I could use a predicate function, though!

Reviewed By: mroch

Differential Revision: D4283070

fbshipit-source-id: b84e7522e8b0f03a90bf5abf6bded48d5bd7fde5

TiddoLangerak/flow,gabro/flow,claudiopro/flow,ForbesLindesay/flow,gabro/flow,claudiopro/flow,mroch/flow,samwgoldman/flow,JonathanUsername/flow,popham/flow,AgentME/flow,gabelevi/flow,samwgoldman/flow,MichaelDeBoey/flow,JonathanUsername/flow,TiddoLangerak/flow,samwgoldman/flow,gabro/flow,JonathanUsername/flow,ylu1317/flow,claudiopro/flow,mroch/flow,mroch/flow,fletcherw/flow,nmote/flow,facebook/flow,JonathanUsername/flow,gabelevi/flow,popham/flow,fletcherw/flow,mroch/flow,JonathanUsername/flow,jamesgpearce/flow,ylu1317/flow,gabelevi/flow,ForbesLindesay/flow,gabro/flow,popham/flow,mroch/flow,popham/flow,popham/flow,ylu1317/flow,gabelevi/flow,fletcherw/flow,ylu1317/flow,gabelevi/flow,MichaelDeBoey/flow,gabro/flow,nmote/flow,AgentME/flow,ForbesLindesay/flow,ylu1317/flow,samwgoldman/flow,AgentME/flow,facebook/flow,popham/flow,ForbesLindesay/flow,jamesgpearce/flow,TiddoLangerak/flow,JonathanUsername/flow,gabelevi/flow,ForbesLindesay/flow,samwgoldman/flow,nmote/flow,ForbesLindesay/flow,MichaelDeBoey/flow,samwgoldman/flow,jamesgpearce/flow,gabelevi/flow,nmote/flow,fletcherw/flow,jamesgpearce/flow,samwgoldman/flow,claudiopro/flow,nmote/flow,fletcherw/flow,facebook/flow,facebook/flow,TiddoLangerak/flow,nmote/flow,AgentME/flow,JonathanUsername/flow,mroch/flow,nmote/flow,facebook/flow,jamesgpearce/flow,gabro/flow,MichaelDeBoey/flow,popham/flow,fletcherw/flow,AgentME/flow,MichaelDeBoey/flow,claudiopro/flow,facebook/flow,TiddoLangerak/flow,facebook/flow,jamesgpearce/flow,jamesgpearce/flow,mroch/flow