style: Move the dirty bit to SheetCollection.
style: Move the dirty bit to SheetCollection.

MozReview-Commit-ID: DO9vv9vmSzF

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