Use a stronger interface to clarify that repeated enumeration is safe
Use a stronger interface to clarify that repeated enumeration is safe

ProcessOutput's members were IEnumerable which could have been very
slow for repeated enumeration. Instead, use IList to guarantee stronger
guarantees.

basoundr/roslyn,AArnott/roslyn,agocke/roslyn,mattscheffer/roslyn,stephentoub/roslyn,Hosch250/roslyn,VSadov/roslyn,dovzhikova/roslyn,OmarTawfik/roslyn,bkoelman/roslyn,KirillOsenkov/roslyn,MattWindsor91/roslyn,jeremymeng/roslyn,dovzhikova/roslyn,Giftednewt/roslyn,ErikSchierboom/roslyn,VitalyTVA/roslyn,yeaicc/roslyn,KiloBravoLima/roslyn,nemec/roslyn,mmitche/roslyn,abock/roslyn,mattscheffer/roslyn,balajikris/roslyn,aelij/roslyn,3F/roslyn,cston/roslyn,Pvlerick/roslyn,tmeschter/roslyn,khyperia/roslyn,doconnell565/roslyn,panopticoncentral/roslyn,natidea/roslyn,jcouv/roslyn,gafter/roslyn,Shiney/roslyn,danielcweber/roslyn,lisong521/roslyn,Inverness/roslyn,AmadeusW/roslyn,brettfo/roslyn,khellang/roslyn,physhi/roslyn,bbarry/roslyn,antonssonj/roslyn,MattWindsor91/roslyn,rgani/roslyn,mattwar/roslyn,antiufo/roslyn,eriawan/roslyn,tmat/roslyn,mmitche/roslyn,VShangxiao/roslyn,sharadagrawal/Roslyn,FICTURE7/roslyn,krishnarajbb/roslyn,3F/roslyn,yjfxfjch/roslyn,nemec/roslyn,panopticoncentral/roslyn,CyrusNajmabadi/roslyn,MattWindsor91/roslyn,jeffanders/roslyn,stebet/roslyn,lisong521/roslyn,Pvlerick/roslyn,paulvanbrenk/roslyn,kelltrick/roslyn,Maxwe11/roslyn,mattscheffer/roslyn,VPashkov/roslyn,xasx/roslyn,DustinCampbell/roslyn,genlu/roslyn,khellang/roslyn,AlexisArce/roslyn,jamesqo/roslyn,KevinH-MS/roslyn,tvand7093/roslyn,jeremymeng/roslyn,dovzhikova/roslyn,Hosch250/roslyn,leppie/roslyn,SeriaWei/roslyn,davkean/roslyn,gafter/roslyn,vcsjones/roslyn,antonssonj/roslyn,AlekseyTs/roslyn,taylorjonl/roslyn,pjmagee/roslyn,zooba/roslyn,ErikSchierboom/roslyn,agocke/roslyn,CyrusNajmabadi/roslyn,AlekseyTs/roslyn,bkoelman/roslyn,CaptainHayashi/roslyn,KirillOsenkov/roslyn,leppie/roslyn,srivatsn/roslyn,jasonmalinowski/roslyn,Giftednewt/roslyn,krishnarajbb/roslyn,jmarolf/roslyn,evilc0des/roslyn,diryboy/roslyn,ilyes14/roslyn,danielcweber/roslyn,tmeschter/roslyn,jroggeman/roslyn,enginekit/roslyn,tmeschter/roslyn,magicbing/roslyn,v-codeel/roslyn,sharadagrawal/Roslyn,drognanar/roslyn,MihaMarkic/roslyn-prank,shyamnamboodiripad/roslyn,antiufo/roslyn,supriyantomaftuh/roslyn,evilc0des/roslyn,magicbing/roslyn,wvdd007/roslyn,jcouv/roslyn,KamalRathnayake/roslyn,devharis/roslyn,zmaruo/roslyn,KevinRansom/roslyn,tvand7093/roslyn,YOTOV-LIMITED/roslyn,VitalyTVA/roslyn,srivatsn/roslyn,shyamnamboodiripad/roslyn,VitalyTVA/roslyn,orthoxerox/roslyn,OmarTawfik/roslyn,Giftednewt/roslyn,moozzyk/roslyn,poizan42/roslyn,akrisiun/roslyn,devharis/roslyn,amcasey/roslyn,oocx/roslyn,yjfxfjch/roslyn,MichalStrehovsky/roslyn,rgani/roslyn,krishnarajbb/roslyn,mgoertz-msft/roslyn,lorcanmooney/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,shyamnamboodiripad/roslyn,michalhosala/roslyn,dpoeschl/roslyn,drognanar/roslyn,robinsedlaczek/roslyn,VPashkov/roslyn,AnthonyDGreen/roslyn,rgani/roslyn,ericfe-ms/roslyn,tang7526/roslyn,natidea/roslyn,supriyantomaftuh/roslyn,EricArndt/roslyn,doconnell565/roslyn,ahmedshuhel/roslyn,tmat/roslyn,MihaMarkic/roslyn-prank,dotnet/roslyn,supriyantomaftuh/roslyn,budcribar/roslyn,aanshibudhiraja/Roslyn,antiufo/roslyn,jbhensley/roslyn,huoxudong125/roslyn,brettfo/roslyn,aelij/roslyn,mseamari/Stuff,jmarolf/roslyn,ahmedshuhel/roslyn,weltkante/roslyn,bartdesmet/roslyn,stebet/roslyn,balajikris/roslyn,nemec/roslyn,ericfe-ms/roslyn,jroggeman/roslyn,grianggrai/roslyn,diryboy/roslyn,sharwell/roslyn,tannergooding/roslyn,MichalStrehovsky/roslyn,OmarTawfik/roslyn,mattwar/roslyn,VShangxiao/roslyn,oocx/roslyn,tannergooding/roslyn,russpowers/roslyn,amcasey/roslyn,AnthonyDGreen/roslyn,paulvanbrenk/roslyn,jamesqo/roslyn,CaptainHayashi/roslyn,panopticoncentral/roslyn,VPashkov/roslyn,Shiney/roslyn,dpoeschl/roslyn,AArnott/roslyn,tmat/roslyn,mgoertz-msft/roslyn,sharwell/roslyn,MatthieuMEZIL/roslyn,natgla/roslyn,basoundr/roslyn,zooba/roslyn,stephentoub/roslyn,Pvlerick/roslyn,diryboy/roslyn,stebet/roslyn,Maxwe11/roslyn,thomaslevesque/roslyn,reaction1989/roslyn,AlexisArce/roslyn,jonatassaraiva/roslyn,khellang/roslyn,3F/roslyn,ericfe-ms/roslyn,akrisiun/roslyn,RipCurrent/roslyn,robinsedlaczek/roslyn,sharadagrawal/Roslyn,mseamari/Stuff,zmaruo/roslyn,jeffanders/roslyn,YOTOV-LIMITED/roslyn,cston/roslyn,DustinCampbell/roslyn,tannergooding/roslyn,orthoxerox/roslyn,VShangxiao/roslyn,drognanar/roslyn,xasx/roslyn,physhi/roslyn,FICTURE7/roslyn,davkean/roslyn,nguerrera/roslyn,michalhosala/roslyn,lorcanmooney/roslyn,vcsjones/roslyn,antonssonj/roslyn,grianggrai/roslyn,jmarolf/roslyn,RipCurrent/roslyn,v-codeel/roslyn,jonatassaraiva/roslyn,SeriaWei/roslyn,KamalRathnayake/roslyn,KevinH-MS/roslyn,Inverness/roslyn,AlekseyTs/roslyn,natidea/roslyn,YOTOV-LIMITED/roslyn,jhendrixMSFT/roslyn,natgla/roslyn,dotnet/roslyn,FICTURE7/roslyn,KevinRansom/roslyn,pdelvo/roslyn,moozzyk/roslyn,lorcanmooney/roslyn,heejaechang/roslyn,jbhensley/roslyn,basoundr/roslyn,AArnott/roslyn,kelltrick/roslyn,xoofx/roslyn,devharis/roslyn,ilyes14/roslyn,pjmagee/roslyn,thomaslevesque/roslyn,xoofx/roslyn,jcouv/roslyn,abock/roslyn,robinsedlaczek/roslyn,ljw1004/roslyn,GuilhermeSa/roslyn,AmadeusW/roslyn,natgla/roslyn,ValentinRueda/roslyn,lisong521/roslyn,EricArndt/roslyn,magicbing/roslyn,budcribar/roslyn,kienct89/roslyn,bbarry/roslyn,MattWindsor91/roslyn,weltkante/roslyn,thomaslevesque/roslyn,oberxon/roslyn,physhi/roslyn,wvdd007/roslyn,bartdesmet/roslyn,zmaruo/roslyn,xasx/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,vslsnap/roslyn,vslsnap/roslyn,russpowers/roslyn,ljw1004/roslyn,pdelvo/roslyn,yeaicc/roslyn,AnthonyDGreen/roslyn,tang7526/roslyn,genlu/roslyn,stephentoub/roslyn,eriawan/roslyn,kienct89/roslyn,ljw1004/roslyn,nguerrera/roslyn,brettfo/roslyn,jeffanders/roslyn,nguerrera/roslyn,danielcweber/roslyn,Maxwe11/roslyn,CaptainHayashi/roslyn,ahmedshuhel/roslyn,HellBrick/roslyn,enginekit/roslyn,AlexisArce/roslyn,khyperia/roslyn,ErikSchierboom/roslyn,grianggrai/roslyn,ilyes14/roslyn,zooba/roslyn,vslsnap/roslyn,bkoelman/roslyn,mavasani/roslyn,amcasey/roslyn,managed-commons/roslyn,oocx/roslyn,cston/roslyn,enginekit/roslyn,doconnell565/roslyn,mseamari/Stuff,swaroop-sridhar/roslyn,HellBrick/roslyn,mgoertz-msft/roslyn,dpoeschl/roslyn,RipCurrent/roslyn,heejaechang/roslyn,Hosch250/roslyn,KiloBravoLima/roslyn,agocke/roslyn,wvdd007/roslyn,sharwell/roslyn,TyOverby/roslyn,jroggeman/roslyn,swaroop-sridhar/roslyn,ValentinRueda/roslyn,jeremymeng/roslyn,aelij/roslyn,managed-commons/roslyn,TyOverby/roslyn,a-ctor/roslyn,GuilhermeSa/roslyn,swaroop-sridhar/roslyn,tvand7093/roslyn,reaction1989/roslyn,huoxudong125/roslyn,AdamSpeight2008/roslyn-AdamSpeight2008,weltkante/roslyn,jasonmalinowski/roslyn,Inverness/roslyn,KevinRansom/roslyn,yeaicc/roslyn,KirillOsenkov/roslyn,russpowers/roslyn,balajikris/roslyn,DustinCampbell/roslyn,jaredpar/roslyn,huoxudong125/roslyn,kienct89/roslyn,paulvanbrenk/roslyn,Shiney/roslyn,mavasani/roslyn,khyperia/roslyn,AmadeusW/roslyn,GuilhermeSa/roslyn,kelltrick/roslyn,jhendrixMSFT/roslyn,jaredpar/roslyn,pdelvo/roslyn,CyrusNajmabadi/roslyn,moozzyk/roslyn,vcsjones/roslyn,jamesqo/roslyn,bbarry/roslyn,taylorjonl/roslyn,KevinH-MS/roslyn,leppie/roslyn,poizan42/roslyn,HellBrick/roslyn,jbhensley/roslyn,mmitche/roslyn,srivatsn/roslyn,VSadov/roslyn,michalhosala/roslyn,gafter/roslyn,yjfxfjch/roslyn,a-ctor/roslyn,budcribar/roslyn,VSadov/roslyn,poizan42/roslyn,dotnet/roslyn,jkotas/roslyn,MichalStrehovsky/roslyn,tang7526/roslyn,xoofx/roslyn,jonatassaraiva/roslyn,a-ctor/roslyn,taylorjonl/roslyn,TyOverby/roslyn,v-codeel/roslyn,aanshibudhiraja/Roslyn,MatthieuMEZIL/roslyn,KiloBravoLima/roslyn,akrisiun/roslyn,bartdesmet/roslyn,EricArndt/roslyn,KamalRathnayake/roslyn,genlu/roslyn,jasonmalinowski/roslyn,managed-commons/roslyn,abock/roslyn,MatthieuMEZIL/roslyn,jkotas/roslyn,MihaMarkic/roslyn-prank,mavasani/roslyn,ValentinRueda/roslyn,mattwar/roslyn,davkean/roslyn,evilc0des/roslyn,orthoxerox/roslyn,pjmagee/roslyn,jaredpar/roslyn,heejaechang/roslyn,jkotas/roslyn,reaction1989/roslyn,oberxon/roslyn,SeriaWei/roslyn,aanshibudhiraja/Roslyn,oberxon/roslyn,jhendrixMSFT/roslyn,eriawan/roslyn