Avoid stylist flushes when sheets are appended and then removed again before flushing layout.
Avoid stylist flushes when sheets are appended and then removed again before flushing layout.

MozReview-Commit-ID: CHgbqfHnjwI

szeged/servo,fiji-flo/servo,pyfisch/servo,cbrewster/servo,avadacatavra/servo,emilio/servo,upsuper/servo,szeged/servo,DominoTree/servo,mattnenterprise/servo,emilio/servo,saneyuki/servo,fiji-flo/servo,jimberlage/servo,szeged/servo,KiChjang/servo,notriddle/servo,sadmansk/servo,nnethercote/servo,DominoTree/servo,DominoTree/servo,szeged/servo,SimonSapin/servo,mbrubeck/servo,saneyuki/servo,cbrewster/servo,paulrouget/servo,mattnenterprise/servo,avadacatavra/servo,pyfisch/servo,peterjoel/servo,avadacatavra/servo,saneyuki/servo,larsbergstrom/servo,nnethercote/servo,DominoTree/servo,cbrewster/servo,avadacatavra/servo,sadmansk/servo,mattnenterprise/servo,notriddle/servo,cbrewster/servo,saneyuki/servo,KiChjang/servo,emilio/servo,DominoTree/servo,DominoTree/servo,jimberlage/servo,splav/servo,cbrewster/servo,fiji-flo/servo,mattnenterprise/servo,jimberlage/servo,SimonSapin/servo,mbrubeck/servo,nnethercote/servo,jimberlage/servo,splav/servo,dati91/servo,paulrouget/servo,peterjoel/servo,upsuper/servo,larsbergstrom/servo,KiChjang/servo,dati91/servo,larsbergstrom/servo,dati91/servo,canaltinova/servo,upsuper/servo,fiji-flo/servo,canaltinova/servo,jimberlage/servo,paulrouget/servo,peterjoel/servo,jimberlage/servo,sadmansk/servo,notriddle/servo,anthgur/servo,notriddle/servo,ConnorGBrewster/servo,splav/servo,mbrubeck/servo,notriddle/servo,KiChjang/servo,larsbergstrom/servo,emilio/servo,saneyuki/servo,szeged/servo,peterjoel/servo,KiChjang/servo,KiChjang/servo,ConnorGBrewster/servo,paulrouget/servo,szeged/servo,dati91/servo,mattnenterprise/servo,splav/servo,larsbergstrom/servo,splav/servo,mattnenterprise/servo,avadacatavra/servo,splav/servo,ConnorGBrewster/servo,sadmansk/servo,paulrouget/servo,anthgur/servo,splav/servo,pyfisch/servo,DominoTree/servo,peterjoel/servo,emilio/servo,canaltinova/servo,mattnenterprise/servo,canaltinova/servo,paulrouget/servo,pyfisch/servo,SimonSapin/servo,anthgur/servo,KiChjang/servo,mbrubeck/servo,larsbergstrom/servo,mbrubeck/servo,emilio/servo,emilio/servo,dati91/servo,ConnorGBrewster/servo,fiji-flo/servo,DominoTree/servo,SimonSapin/servo,mbrubeck/servo,peterjoel/servo,nnethercote/servo,larsbergstrom/servo,szeged/servo,nnethercote/servo,jimberlage/servo,cbrewster/servo,jimberlage/servo,dati91/servo,fiji-flo/servo,saneyuki/servo,peterjoel/servo,KiChjang/servo,KiChjang/servo,peterjoel/servo,ConnorGBrewster/servo,avadacatavra/servo,KiChjang/servo,pyfisch/servo,szeged/servo,saneyuki/servo,anthgur/servo,nnethercote/servo,sadmansk/servo,nnethercote/servo,anthgur/servo,pyfisch/servo,pyfisch/servo,nnethercote/servo,notriddle/servo,canaltinova/servo,larsbergstrom/servo,anthgur/servo,notriddle/servo,sadmansk/servo,nnethercote/servo,anthgur/servo,larsbergstrom/servo,cbrewster/servo,paulrouget/servo,avadacatavra/servo,splav/servo,sadmansk/servo,notriddle/servo,SimonSapin/servo,dati91/servo,anthgur/servo,upsuper/servo,DominoTree/servo,saneyuki/servo,upsuper/servo,emilio/servo,upsuper/servo,pyfisch/servo,mattnenterprise/servo,canaltinova/servo,SimonSapin/servo,emilio/servo,canaltinova/servo,nnethercote/servo,pyfisch/servo,avadacatavra/servo,SimonSapin/servo,splav/servo,ConnorGBrewster/servo,notriddle/servo,SimonSapin/servo,jimberlage/servo,szeged/servo,sadmansk/servo,mbrubeck/servo,paulrouget/servo,peterjoel/servo,emilio/servo,upsuper/servo,ConnorGBrewster/servo,dati91/servo,fiji-flo/servo,DominoTree/servo,upsuper/servo,pyfisch/servo,larsbergstrom/servo,mbrubeck/servo,canaltinova/servo,notriddle/servo,szeged/servo,saneyuki/servo,peterjoel/servo,ConnorGBrewster/servo,paulrouget/servo,paulrouget/servo,fiji-flo/servo,splav/servo,saneyuki/servo,cbrewster/servo