Auto merge of #18406 - servo:cleanup-media, r=emilio
Auto merge of #18406 - servo:cleanup-media, r=emilio

Start cleaning up HTMLMediaElement a bit

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