style: Don't skip computation of pseudo-elements of display: none elements.
style: Don't skip computation of pseudo-elements of display: none elements.

We have optimizations to avoid doing selector-matching when the style attribute
changes, so, given you can toggle the display property and the pseudo-elements
will suddenly become effective, we can't really skip them.

Furthermore, we assume that if an element has an ElementStyles, they're
up-to-date and we can use them for getComputedStyle, so it's pretty easy to
prove that we do the wrong thing when calling getComputedStyle with a
pseudo-element on a display: none root.

Bug: 1384065
Reviewed-by: heycam
MozReview-Commit-ID: BIOqevGZyrm

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