Auto merge of #8552 - michaelwu:avoid_overflow, r=glennw
Auto merge of #8552 - michaelwu:avoid_overflow, r=glennw

Avoid overflow in freetype/font_context.rs

When new_actual_size < old_actual_size, there is an overflow panic since we're using usize. This breaks Reddit for me.

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