auto merge of #2602 : mbrubeck/servo/revert-root-pipeline-check, r=pcwalton
auto merge of #2602 : mbrubeck/servo/revert-root-pipeline-check, r=pcwalton

This reverts 2b0134be7bb8a4372f1a8703b5a1b114e65351f6 because it was not correct for iframes.  Oops.  (Wasn't caught by tests because we still have other crashes preventing iframe testing.)  r? @pcwalton.

mukilan/servo,hyowon/servo,rnestler/servo,jgraham/servo,huonw/servo,anthgur/servo,larsbergstrom/servo,A-deLuna/servo,mukilan/servo,RenaudParis/servo,rixrix/servo,samfoo/servo,dmarcos/servo,shrenikgala/servo,eddyb/servo,jlegendary/servo,Adenilson/prototype-viewing-distance,steveklabnik/servo,DominoTree/servo,jlegendary/servo,fiji-flo/servo,indykish/servo,wpgallih/servo,jdramani/servo,aidanhs/servo,aweinstock314/servo,notriddle/servo,ruud-v-a/servo,meh/servo,jimberlage/servo,aweinstock314/servo,wartman4404/servo,akosel/servo,saratang/servo,karlito40/servo,fiji-flo/servo,pgonda/servo,RenaudParis/servo,wpgallih/servo,rentongzhang/servo,thiagopnts/servo,bfrohs/servo,youprofit/servo,wartman4404/servo,sadmansk/servo,jdramani/servo,dagnir/servo,peterjoel/servo,juzer10/servo,eddyb/servo,aweinstock314/servo,echochamber/servo,pyecs/servo,j3parker/servo,GreenRecycleBin/servo,sadmansk/servo,bjwbell/servo,hyowon/servo,anthgur/servo,SimonSapin/servo,luniv/servo,jgraham/servo,aidanhs/servo,brendandahl/servo,WriterOfAlicrow/servo,caldwell/servo,caldwell/servo,chotchki/servo,hyowon/servo,canaltinova/servo,codemac/servo,pgonda/servo,mbrubeck/servo,splav/servo,mdibaiee/servo,ConnorGBrewster/servo,codemac/servo,avadacatavra/servo,bjwbell/servo,snf/servo,luniv/servo,huonw/servo,dvberkel/servo,dati91/servo,srbhklkrn/SERVOENGINE,KiChjang/servo,anthgur/servo,SimonSapin/servo,canaltinova/servo,zhangjunlei26/servo,sadmansk/servo,mukilan/servo,ryancanhelpyou/servo,samfoo/servo,dsandeephegde/servo,brendandahl/servo,pyfisch/servo,tafia/servo,dagnir/servo,huonw/servo,A-deLuna/servo,rnestler/servo,avadacatavra/servo,samfoo/servo,shrenikgala/servo,avadacatavra/servo,srbhklkrn/SERVOENGINE,jimberlage/servo,DominoTree/servo,michaelwu/servo,huonw/servo,A-deLuna/servo,splav/servo,GreenRecycleBin/servo,jgraham/servo,emilio/servo,evilpie/servo,deokjinkim/servo,sadmansk/servo,nnethercote/servo,CJ8664/servo,youprofit/servo,paulrouget/servo,DominoTree/servo,chotchki/servo,aidanhs/servo,wpgallih/servo,dhananjay92/servo,tafia/servo,GreenRecycleBin/servo,kindersung/servo,deokjinkim/servo,nnethercote/servo,s142857/servo,dagnir/servo,zhangjunlei26/servo,AnthonyBroadCrawford/servo,canaltinova/servo,dati91/servo,luniv/servo,dhananjay92/servo,tempbottle/servo,eddyb/servo,KiChjang/servo,runarberg/servo,cbrewster/servo,splav/servo,upsuper/servo,mattnenterprise/servo,dati91/servo,mt2d2/servo,luniv/servo,jdramani/servo,jgraham/servo,canaltinova/servo,nerith/servo,WriterOfAlicrow/servo,nick-thompson/servo,tafia/servo,walac/servo,saneyuki/servo,pyecs/servo,AnthonyBroadCrawford/servo,CJ8664/servo,dmarcos/servo,KiChjang/servo,pgonda/servo,GyrosOfWar/servo,aidanhs/servo,peterjoel/servo,tschneidereit/servo,indykish/servo,evilpie/servo,froydnj/servo,larsbergstrom/servo,echochamber/servo,nerith/servo,deokjinkim/servo,tschneidereit/servo,walac/servo,paulrouget/servo,walac/servo,dmarcos/servo,rentongzhang/servo,brendandahl/servo,saneyuki/servo,hyowon/servo,thiagopnts/servo,jimberlage/servo,hyowon/servo,notriddle/servo,meh/servo,bfrohs/servo,larsbergstrom/servo,anthgur/servo,chotchki/servo,dati91/servo,pyecs/servo,srbhklkrn/SERVOENGINE,akosel/servo,sadmansk/servo,dvberkel/servo,szeged/servo,DominoTree/servo,juzer10/servo,brendandahl/servo,froydnj/servo,SimonSapin/servo,cbrewster/servo,emilio/servo,walac/servo,kindersung/servo,anthgur/servo,paulrouget/servo,jimberlage/servo,avadacatavra/servo,RenaudParis/servo,runarberg/servo,dsandeephegde/servo,WriterOfAlicrow/servo,mbrubeck/servo,upsuper/servo,echochamber/servo,nick-thompson/servo,WriterOfAlicrow/servo,sadmansk/servo,eddyb/servo,jimberlage/servo,canaltinova/servo,emilio/servo,g-k/servo,Adenilson/prototype-viewing-distance,tempbottle/servo,peterjoel/servo,tafia/servo,cbrewster/servo,jimberlage/servo,akosel/servo,dvberkel/servo,wartman4404/servo,samfoo/servo,GyrosOfWar/servo,meh/servo,wartman4404/servo,dhananjay92/servo,seanmonstar/servo,ConnorGBrewster/servo,ConnorGBrewster/servo,paulrouget/servo,ConnorGBrewster/servo,vks/servo,nnethercote/servo,KiChjang/servo,saneyuki/servo,szeged/servo,dsandeephegde/servo,nnethercote/servo,rixrix/servo,Shraddha512/servo,nrc/servo,meh/servo,pgonda/servo,WriterOfAlicrow/servo,echochamber/servo,anthgur/servo,dagnir/servo,jdramani/servo,nerith/servo,bfrohs/servo,caldwell/servo,aweinstock314/servo,dagnir/servo,chotchki/servo,nrc/servo,meh/servo,splav/servo,walac/servo,rixrix/servo,evilpie/servo,bjwbell/servo,szeged/servo,huonw/servo,zhangjunlei26/servo,mdibaiee/servo,avadacatavra/servo,j3parker/servo,zentner-kyle/servo,codemac/servo,samfoo/servo,sadmansk/servo,jgraham/servo,seanmonstar/servo,nerith/servo,ruud-v-a/servo,tempbottle/servo,nerith/servo,bjwbell/servo,mbrubeck/servo,nrc/servo,saneyuki/servo,dati91/servo,thiagopnts/servo,runarberg/servo,mt2d2/servo,wpgallih/servo,jdramani/servo,saneyuki/servo,boghison/servo,ruud-v-a/servo,dsandeephegde/servo,g-k/servo,nrc/servo,j3parker/servo,wpgallih/servo,paulrouget/servo,mattnenterprise/servo,szeged/servo,rnestler/servo,splav/servo,peterjoel/servo,notriddle/servo,avadacatavra/servo,jimberlage/servo,dhananjay92/servo,bfrohs/servo,boghison/servo,kindersung/servo,anthgur/servo,evilpie/servo,ryancanhelpyou/servo,KiChjang/servo,tempbottle/servo,pyfisch/servo,s142857/servo,pyfisch/servo,fiji-flo/servo,youprofit/servo,luniv/servo,nick-thompson/servo,s142857/servo,cbrewster/servo,nick-thompson/servo,boghison/servo,rnestler/servo,nick-thompson/servo,steveklabnik/servo,zhangjunlei26/servo,juzer10/servo,thiagopnts/servo,dati91/servo,larsbergstrom/servo,indykish/servo,pgonda/servo,samfoo/servo,hyowon/servo,Adenilson/prototype-viewing-distance,vks/servo,paulrouget/servo,avadacatavra/servo,A-deLuna/servo,g-k/servo,aidanhs/servo,A-deLuna/servo,Shraddha512/servo,evilpie/servo,SimonSapin/servo,ryancanhelpyou/servo,Shraddha512/servo,kindersung/servo,vks/servo,pyfisch/servo,Shraddha512/servo,runarberg/servo,jgraham/servo,RenaudParis/servo,evilpie/servo,nnethercote/servo,froydnj/servo,echochamber/servo,g-k/servo,karlito40/servo,larsbergstrom/servo,nrc/servo,g-k/servo,j3parker/servo,splav/servo,RenaudParis/servo,froydnj/servo,jlegendary/servo,pyfisch/servo,saneyuki/servo,rentongzhang/servo,boghison/servo,mt2d2/servo,froydnj/servo,mukilan/servo,upsuper/servo,zhangjunlei26/servo,rnestler/servo,larsbergstrom/servo,dati91/servo,peterjoel/servo,snf/servo,nrc/servo,pyfisch/servo,brendandahl/servo,nerith/servo,szeged/servo,mattnenterprise/servo,seanmonstar/servo,boghison/servo,michaelwu/servo,AnthonyBroadCrawford/servo,SimonSapin/servo,huonw/servo,j3parker/servo,CJ8664/servo,bfrohs/servo,CJ8664/servo,GreenRecycleBin/servo,seanmonstar/servo,dvberkel/servo,Adenilson/prototype-viewing-distance,paulrouget/servo,thiagopnts/servo,tschneidereit/servo,rentongzhang/servo,saratang/servo,DominoTree/servo,tafia/servo,akosel/servo,saratang/servo,boghison/servo,nnethercote/servo,ruud-v-a/servo,mattnenterprise/servo,shrenikgala/servo,pgonda/servo,Shraddha512/servo,pyecs/servo,pyfisch/servo,aweinstock314/servo,rixrix/servo,ryancanhelpyou/servo,dvberkel/servo,notriddle/servo,thiagopnts/servo,ConnorGBrewster/servo,szeged/servo,tempbottle/servo,aidanhs/servo,bjwbell/servo,steveklabnik/servo,SimonSapin/servo,mbrubeck/servo,cbrewster/servo,mattnenterprise/servo,ConnorGBrewster/servo,bjwbell/servo,notriddle/servo,bjwbell/servo,juzer10/servo,emilio/servo,notriddle/servo,paulrouget/servo,snf/servo,nick-thompson/servo,youprofit/servo,GyrosOfWar/servo,DominoTree/servo,nnethercote/servo,steveklabnik/servo,karlito40/servo,jdramani/servo,tschneidereit/servo,splav/servo,anthgur/servo,notriddle/servo,paulrouget/servo,nerith/servo,nnethercote/servo,runarberg/servo,runarberg/servo,mbrubeck/servo,j3parker/servo,saratang/servo,DominoTree/servo,eddyb/servo,SimonSapin/servo,vks/servo,GreenRecycleBin/servo,dati91/servo,zhangjunlei26/servo,rentongzhang/servo,AnthonyBroadCrawford/servo,splav/servo,seanmonstar/servo,snf/servo,nnethercote/servo,evilpie/servo,cbrewster/servo,peterjoel/servo,chotchki/servo,michaelwu/servo,wartman4404/servo,DominoTree/servo,mbrubeck/servo,deokjinkim/servo,ryancanhelpyou/servo,saneyuki/servo,vks/servo,GyrosOfWar/servo,rnestler/servo,runarberg/servo,saneyuki/servo,pyfisch/servo,thiagopnts/servo,walac/servo,meh/servo,aweinstock314/servo,indykish/servo,akosel/servo,echochamber/servo,ruud-v-a/servo,caldwell/servo,s142857/servo,zentner-kyle/servo,dsandeephegde/servo,GreenRecycleBin/servo,indykish/servo,ryancanhelpyou/servo,wpgallih/servo,michaelwu/servo,deokjinkim/servo,pyecs/servo,CJ8664/servo,tafia/servo,upsuper/servo,brendandahl/servo,vks/servo,Adenilson/prototype-viewing-distance,s142857/servo,aidanhs/servo,michaelwu/servo,kindersung/servo,rentongzhang/servo,dhananjay92/servo,saratang/servo,GyrosOfWar/servo,zentner-kyle/servo,pyfisch/servo,karlito40/servo,indykish/servo,rentongzhang/servo,DominoTree/servo,mdibaiee/servo,peterjoel/servo,eddyb/servo,srbhklkrn/SERVOENGINE,cbrewster/servo,Shraddha512/servo,dmarcos/servo,canaltinova/servo,dsandeephegde/servo,pyfisch/servo,CJ8664/servo,deokjinkim/servo,mattnenterprise/servo,ConnorGBrewster/servo,splav/servo,snf/servo,Shraddha512/servo,mdibaiee/servo,CJ8664/servo,rnestler/servo,dhananjay92/servo,jimberlage/servo,caldwell/servo,upsuper/servo,echochamber/servo,eddyb/servo,Adenilson/prototype-viewing-distance,luniv/servo,wpgallih/servo,mattnenterprise/servo,mt2d2/servo,dvberkel/servo,zhangjunlei26/servo,dmarcos/servo,shrenikgala/servo,pgonda/servo,indykish/servo,szeged/servo,mbrubeck/servo,j3parker/servo,emilio/servo,thiagopnts/servo,rixrix/servo,peterjoel/servo,A-deLuna/servo,snf/servo,tschneidereit/servo,dsandeephegde/servo,tschneidereit/servo,saratang/servo,peterjoel/servo,fiji-flo/servo,juzer10/servo,tschneidereit/servo,jimberlage/servo,tempbottle/servo,snf/servo,KiChjang/servo,jdramani/servo,fiji-flo/servo,rixrix/servo,shrenikgala/servo,emilio/servo,KiChjang/servo,WriterOfAlicrow/servo,tempbottle/servo,kindersung/servo,RenaudParis/servo,DominoTree/servo,paulrouget/servo,emilio/servo,dhananjay92/servo,bfrohs/servo,steveklabnik/servo,zhangjunlei26/servo,splav/servo,kindersung/servo,KiChjang/servo,pyecs/servo,caldwell/servo,wpgallih/servo,dmarcos/servo,zentner-kyle/servo,nrc/servo,zentner-kyle/servo,mattnenterprise/servo,luniv/servo,wpgallih/servo,RenaudParis/servo,s142857/servo,codemac/servo,codemac/servo,steveklabnik/servo,AnthonyBroadCrawford/servo,vks/servo,michaelwu/servo,srbhklkrn/SERVOENGINE,jgraham/servo,fiji-flo/servo,GyrosOfWar/servo,KiChjang/servo,avadacatavra/servo,KiChjang/servo,SimonSapin/servo,wartman4404/servo,mdibaiee/servo,mdibaiee/servo,notriddle/servo,mbrubeck/servo,shrenikgala/servo,emilio/servo,mt2d2/servo,wartman4404/servo,zentner-kyle/servo,rixrix/servo,brendandahl/servo,fiji-flo/servo,juzer10/servo,srbhklkrn/SERVOENGINE,rixrix/servo,szeged/servo,saratang/servo,upsuper/servo,jlegendary/servo,canaltinova/servo,youprofit/servo,g-k/servo,CJ8664/servo,mt2d2/servo,dsandeephegde/servo,canaltinova/servo,saneyuki/servo,emilio/servo,eddyb/servo,emilio/servo,karlito40/servo,pyecs/servo,rixrix/servo,dvberkel/servo,ryancanhelpyou/servo,saneyuki/servo,juzer10/servo,srbhklkrn/SERVOENGINE,froydnj/servo,sadmansk/servo,dagnir/servo,mukilan/servo,zhangjunlei26/servo,AnthonyBroadCrawford/servo,GreenRecycleBin/servo,cbrewster/servo,larsbergstrom/servo,peterjoel/servo,evilpie/servo,upsuper/servo,indykish/servo,AnthonyBroadCrawford/servo,fiji-flo/servo,dagnir/servo,s142857/servo,jlegendary/servo,ruud-v-a/servo,szeged/servo,A-deLuna/servo,g-k/servo,aweinstock314/servo,upsuper/servo,Adenilson/prototype-viewing-distance,chotchki/servo,zentner-kyle/servo,youprofit/servo,meh/servo,GreenRecycleBin/servo,hyowon/servo,larsbergstrom/servo,mukilan/servo,boghison/servo,rnestler/servo,caldwell/servo,szeged/servo,youprofit/servo,GreenRecycleBin/servo,walac/servo,karlito40/servo,mt2d2/servo,seanmonstar/servo,dmarcos/servo,nnethercote/servo,nick-thompson/servo,larsbergstrom/servo,samfoo/servo,akosel/servo,notriddle/servo,karlito40/servo,larsbergstrom/servo,WriterOfAlicrow/servo,jlegendary/servo,jlegendary/servo,deokjinkim/servo,akosel/servo,notriddle/servo,codemac/servo,ConnorGBrewster/servo,codemac/servo,evilpie/servo,mdibaiee/servo,GyrosOfWar/servo,huonw/servo,tafia/servo,shrenikgala/servo,indykish/servo,steveklabnik/servo