memoize file_depends_on, speeds up incremental
memoize file_depends_on, speeds up incremental

Summary: this runs through every dependency of every file. the stack was preventing cycles, but not helping with exponential growth. this adds the memoization that used to be there back in, except it's per file to deal with cycles.

Reviewed By: @bhosmer

Differential Revision: D2331709

AprilArcus/flow,claudiopro/flow,KevinTCoughlin/flow,mroch/flow,samwgoldman/flow,facebook/flow,d14b3l/flow,d14b3l/flow,jeffmo/flow,darioajr/flow,dv/flow,jeffmo/flow,JonathanUsername/flow,jamesgpearce/flow,jeffutter/flow,gabelevi/flow,dv/flow,jgrund/flow,Drooids/flow,graue/flow,fletcherw/flow,rafaelstz/flow,JohnyDays/flow,facebook/flow,mroch/flow,popham/flow,popham/flow,AprilArcus/flow,JonathanUsername/flow,jgrund/flow,Fresheyeball/flow,fletcherw/flow,MichaelDeBoey/flow,popham/flow,samwgoldman/flow,ForbesLindesay/flow,popham/flow,jeffmo/flow,jamesgpearce/flow,chenglou/flow,paulshen/flow,cesarandreu/flow,fletcherw/flow,siddhartharay007/flow,AgentME/flow,popham/flow,popham/flow,shiftcars/flow,mcanthony/flow-type,danvk/flow,jgrund/flow,rafaelstz/flow,rafaelstz/flow,lyip1992/flow,d14b3l/flow,nmote/flow,Eyyub/flow,lyip1992/flow,TiddoLangerak/flow,ForbesLindesay/flow,mroch/flow,samwgoldman/flow,Fresheyeball/flow,Fresheyeball/flow,danvk/flow,nmote/flow,Wanderfalke/flow,gabro/flow,asivitz/flow,Drooids/flow,chenglou/flow,claudiopro/flow,gabelevi/flow,samwgoldman/flow,gabro/flow,facebook/flow,jamesgpearce/flow,ForbesLindesay/flow,JohnyDays/flow,mroch/flow,CJstar/flow,mroch/flow,lyip1992/flow,darioajr/flow,Wanderfalke/flow,dv/flow,mcanthony/flow-type,claudiopro/flow,samwgoldman/flow,MichaelDeBoey/flow,ylu1317/flow,AprilArcus/flow,Drooids/flow,mroch/flow,jdelStrother/flow,jdelStrother/flow,paulshen/flow,gabelevi/flow,asivitz/flow,TiddoLangerak/flow,jdelStrother/flow,shiftcars/flow,fletcherw/flow,jgrund/flow,jamesgpearce/flow,rafaelstz/flow,jeffutter/flow,siddhartharay007/flow,chenglou/flow,fletcherw/flow,Wanderfalke/flow,d14b3l/flow,gabro/flow,KevinTCoughlin/flow,samwgoldman/flow,gabro/flow,claudiopro/flow,MichaelDeBoey/flow,paulshen/flow,gabro/flow,nmote/flow,ianobermiller/flow,JohnyDays/flow,samwgoldman/flow,popham/flow,jgrund/flow,KevinTCoughlin/flow,d14b3l/flow,shiftcars/flow,siddhartharay007/flow,siddhartharay007/flow,JonathanUsername/flow,facebook/flow,chenglou/flow,ylu1317/flow,asivitz/flow,jamesgpearce/flow,jgrund/flow,cesarandreu/flow,facebook/flow,jeffmo/flow,MichaelDeBoey/flow,fletcherw/flow,OCamlPro/flow,OCamlPro/flow,graue/flow,jeffmo/flow,claudiopro/flow,nmote/flow,jdelStrother/flow,rafaelstz/flow,jeffmo/flow,gabelevi/flow,chenglou/flow,OCamlPro/flow,mroch/flow,AgentME/flow,darioajr/flow,TiddoLangerak/flow,CJstar/flow,mcanthony/flow-type,shiftcars/flow,cesarandreu/flow,gabelevi/flow,d14b3l/flow,jeffutter/flow,jdelStrother/flow,danvk/flow,ForbesLindesay/flow,danvk/flow,ianobermiller/flow,dv/flow,graue/flow,JonathanUsername/flow,AgentME/flow,JohnyDays/flow,jdelStrother/flow,CJstar/flow,Eyyub/flow,ylu1317/flow,gabelevi/flow,jamesgpearce/flow,nmote/flow,AprilArcus/flow,Fresheyeball/flow,graue/flow,AgentME/flow,CJstar/flow,Drooids/flow,shiftcars/flow,ianobermiller/flow,nmote/flow,AprilArcus/flow,ForbesLindesay/flow,graue/flow,jamesgpearce/flow,AprilArcus/flow,TiddoLangerak/flow,paulshen/flow,jeffutter/flow,JonathanUsername/flow,facebook/flow,mcanthony/flow-type,TiddoLangerak/flow,JonathanUsername/flow,chenglou/flow,graue/flow,asivitz/flow,facebook/flow,OCamlPro/flow,AgentME/flow,shiftcars/flow,ylu1317/flow,KevinTCoughlin/flow,Wanderfalke/flow,gabro/flow,Eyyub/flow,ianobermiller/flow,lyip1992/flow,ylu1317/flow,ForbesLindesay/flow,Eyyub/flow,darioajr/flow,cesarandreu/flow,MichaelDeBoey/flow,gabelevi/flow,JonathanUsername/flow,nmote/flow