Fix dynamic restyling that changes whether our element may generate a pseudo to clear out stale pseudo styles.
Fix dynamic restyling that changes whether our element may generate a pseudo to clear out stale pseudo styles.

Gecko bug 1324618 part 1: https://bugzilla.mozilla.org/show_bug.cgi?id=1324618

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