Auto merge of #9425 - connorimes:characterize-use-output-png, r=larsbergstrom
Auto merge of #9425 - connorimes:characterize-use-output-png, r=larsbergstrom

Output to png file since exit flag doesn't work

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.svg" height="40" alt="Review on Reviewable"/>](https://reviewable.io/reviews/servo/servo/9425)
<!-- Reviewable:end -->

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