Fix for parallel data race in layout code. Fixes #2308.
Fix for parallel data race in layout code. Fixes #2308.

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