style: Prevent cousin sharing if we haven't restyled the parents.
style: Prevent cousin sharing if we haven't restyled the parents.

This "fixes" bug 1381821 by disabling the optimization in the cases we can't
prove this is correct. Bug 1387116 tracks fixing the optimization to apply more
broadly.

Bug: 1381821
Reviewed-by: bz
MozReview-Commit-ID: COKdmHHokGx

DominoTree/servo,saneyuki/servo,thiagopnts/servo,notriddle/servo,sadmansk/servo,thiagopnts/servo,mbrubeck/servo,cbrewster/servo,dsandeephegde/servo,rnestler/servo,szeged/servo,jimberlage/servo,eddyb/servo,dsandeephegde/servo,szeged/servo,eddyb/servo,dsandeephegde/servo,KiChjang/servo,cbrewster/servo,fiji-flo/servo,sadmansk/servo,larsbergstrom/servo,avadacatavra/servo,nnethercote/servo,mattnenterprise/servo,anthgur/servo,dati91/servo,canaltinova/servo,emilio/servo,anthgur/servo,saneyuki/servo,notriddle/servo,upsuper/servo,upsuper/servo,paulrouget/servo,jimberlage/servo,KiChjang/servo,SimonSapin/servo,mattnenterprise/servo,dati91/servo,paulrouget/servo,dsandeephegde/servo,CJ8664/servo,peterjoel/servo,KiChjang/servo,dati91/servo,splav/servo,nnethercote/servo,upsuper/servo,pyfisch/servo,thiagopnts/servo,anthgur/servo,emilio/servo,sadmansk/servo,saneyuki/servo,splav/servo,SimonSapin/servo,DominoTree/servo,szeged/servo,nnethercote/servo,saneyuki/servo,peterjoel/servo,thiagopnts/servo,dsandeephegde/servo,sadmansk/servo,nnethercote/servo,emilio/servo,cbrewster/servo,fiji-flo/servo,canaltinova/servo,canaltinova/servo,DominoTree/servo,nnethercote/servo,KiChjang/servo,pyfisch/servo,pyfisch/servo,dsandeephegde/servo,fiji-flo/servo,peterjoel/servo,ConnorGBrewster/servo,cbrewster/servo,jimberlage/servo,nnethercote/servo,pyfisch/servo,pyfisch/servo,splav/servo,eddyb/servo,canaltinova/servo,emilio/servo,fiji-flo/servo,dati91/servo,eddyb/servo,upsuper/servo,sadmansk/servo,ConnorGBrewster/servo,upsuper/servo,emilio/servo,anthgur/servo,dati91/servo,paulrouget/servo,paulrouget/servo,mattnenterprise/servo,nnethercote/servo,larsbergstrom/servo,fiji-flo/servo,mbrubeck/servo,jimberlage/servo,peterjoel/servo,SimonSapin/servo,mattnenterprise/servo,splav/servo,splav/servo,pyfisch/servo,larsbergstrom/servo,paulrouget/servo,jimberlage/servo,avadacatavra/servo,DominoTree/servo,avadacatavra/servo,fiji-flo/servo,notriddle/servo,rnestler/servo,KiChjang/servo,avadacatavra/servo,jimberlage/servo,peterjoel/servo,CJ8664/servo,splav/servo,cbrewster/servo,pyfisch/servo,szeged/servo,paulrouget/servo,KiChjang/servo,cbrewster/servo,splav/servo,paulrouget/servo,paulrouget/servo,CJ8664/servo,mbrubeck/servo,rnestler/servo,dsandeephegde/servo,ConnorGBrewster/servo,anthgur/servo,sadmansk/servo,larsbergstrom/servo,sadmansk/servo,KiChjang/servo,mattnenterprise/servo,canaltinova/servo,avadacatavra/servo,paulrouget/servo,ConnorGBrewster/servo,fiji-flo/servo,larsbergstrom/servo,mattnenterprise/servo,avadacatavra/servo,avadacatavra/servo,dati91/servo,canaltinova/servo,SimonSapin/servo,rnestler/servo,szeged/servo,notriddle/servo,KiChjang/servo,emilio/servo,saneyuki/servo,anthgur/servo,nnethercote/servo,KiChjang/servo,DominoTree/servo,peterjoel/servo,saneyuki/servo,jimberlage/servo,emilio/servo,splav/servo,szeged/servo,szeged/servo,rnestler/servo,emilio/servo,ConnorGBrewster/servo,pyfisch/servo,notriddle/servo,larsbergstrom/servo,upsuper/servo,splav/servo,DominoTree/servo,rnestler/servo,notriddle/servo,szeged/servo,mbrubeck/servo,SimonSapin/servo,dsandeephegde/servo,peterjoel/servo,thiagopnts/servo,upsuper/servo,thiagopnts/servo,CJ8664/servo,eddyb/servo,eddyb/servo,pyfisch/servo,dati91/servo,dati91/servo,pyfisch/servo,saneyuki/servo,mbrubeck/servo,larsbergstrom/servo,cbrewster/servo,notriddle/servo,ConnorGBrewster/servo,paulrouget/servo,SimonSapin/servo,DominoTree/servo,CJ8664/servo,szeged/servo,larsbergstrom/servo,anthgur/servo,SimonSapin/servo,emilio/servo,SimonSapin/servo,mattnenterprise/servo,larsbergstrom/servo,mbrubeck/servo,peterjoel/servo,thiagopnts/servo,canaltinova/servo,mbrubeck/servo,notriddle/servo,nnethercote/servo,sadmansk/servo,avadacatavra/servo,rnestler/servo,saneyuki/servo,CJ8664/servo,cbrewster/servo,larsbergstrom/servo,emilio/servo,upsuper/servo,peterjoel/servo,jimberlage/servo,thiagopnts/servo,mbrubeck/servo,peterjoel/servo,CJ8664/servo,ConnorGBrewster/servo,szeged/servo,mattnenterprise/servo,notriddle/servo,canaltinova/servo,KiChjang/servo,saneyuki/servo,jimberlage/servo,eddyb/servo,DominoTree/servo,fiji-flo/servo,rnestler/servo,saneyuki/servo,nnethercote/servo,DominoTree/servo,eddyb/servo,CJ8664/servo,splav/servo,DominoTree/servo,ConnorGBrewster/servo,anthgur/servo,notriddle/servo