Don't force reflow on content changes
Don't force reflow on content changes

This fixes a performance regression caused by the previous patches.  Once we
allowed script and layout to run during parsing, it was running too often
(every time the document changed and called window.reflow).

Fixes #1269.

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