Implement correct security checks for HTMLIFrameElement::contentDocument.
Implement correct security checks for HTMLIFrameElement::contentDocument.

Fixes #10964.

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