auto merge of #5403 : frewsxcv/servo/cookie-default-path, r=jdm
auto merge of #5403 : frewsxcv/servo/cookie-default-path, r=jdm

* Previously, the function returned an owned String, which is not
  necessary, so now it returns a slice
* Steps have now been documented/labeled
* The last step of the algorithm was incorrect; it would only slice the
  path if the "/" was the last character, which is not what the spec
  says. The spec says to slice up until (but not including) the last
  "/". Also added a regression test for this.

tschneidereit/servo,paulrouget/servo,zhangjunlei26/servo,peterjoel/servo,CJ8664/servo,rixrix/servo,dvberkel/servo,anthgur/servo,akosel/servo,szeged/servo,steveklabnik/servo,pgonda/servo,fiji-flo/servo,rentongzhang/servo,jdramani/servo,indykish/servo,boghison/servo,pyfisch/servo,emilio/servo,aweinstock314/servo,s142857/servo,AnthonyBroadCrawford/servo,hyowon/servo,runarberg/servo,ConnorGBrewster/servo,KiChjang/servo,szeged/servo,nrc/servo,hyowon/servo,CJ8664/servo,dati91/servo,indykish/servo,thiagopnts/servo,tschneidereit/servo,karlito40/servo,paulrouget/servo,youprofit/servo,KiChjang/servo,dsandeephegde/servo,brendandahl/servo,GreenRecycleBin/servo,emilio/servo,mt2d2/servo,aidanhs/servo,pyfisch/servo,notriddle/servo,SimonSapin/servo,meh/servo,nick-thompson/servo,CJ8664/servo,peterjoel/servo,codemac/servo,jgraham/servo,jimberlage/servo,cbrewster/servo,GreenRecycleBin/servo,nerith/servo,samfoo/servo,wartman4404/servo,larsbergstrom/servo,pyfisch/servo,cbrewster/servo,DominoTree/servo,upsuper/servo,ryancanhelpyou/servo,samfoo/servo,brendandahl/servo,pgonda/servo,meh/servo,ConnorGBrewster/servo,paulrouget/servo,steveklabnik/servo,WriterOfAlicrow/servo,thiagopnts/servo,runarberg/servo,GreenRecycleBin/servo,emilio/servo,dagnir/servo,eddyb/servo,pyfisch/servo,upsuper/servo,emilio/servo,DominoTree/servo,eddyb/servo,jdramani/servo,anthgur/servo,avadacatavra/servo,pyecs/servo,dhananjay92/servo,g-k/servo,tschneidereit/servo,jimberlage/servo,A-deLuna/servo,saneyuki/servo,nrc/servo,dagnir/servo,DominoTree/servo,paulrouget/servo,boghison/servo,jlegendary/servo,saratang/servo,g-k/servo,peterjoel/servo,pgonda/servo,pyecs/servo,KiChjang/servo,vks/servo,nick-thompson/servo,codemac/servo,deokjinkim/servo,vks/servo,upsuper/servo,dati91/servo,zentner-kyle/servo,s142857/servo,youprofit/servo,sadmansk/servo,huonw/servo,splav/servo,peterjoel/servo,RenaudParis/servo,canaltinova/servo,karlito40/servo,nick-thompson/servo,rentongzhang/servo,WriterOfAlicrow/servo,emilio/servo,pyfisch/servo,rnestler/servo,KiChjang/servo,rixrix/servo,youprofit/servo,KiChjang/servo,aweinstock314/servo,aidanhs/servo,avadacatavra/servo,A-deLuna/servo,tafia/servo,g-k/servo,thiagopnts/servo,jgraham/servo,ConnorGBrewster/servo,GreenRecycleBin/servo,mbrubeck/servo,samfoo/servo,karlito40/servo,ConnorGBrewster/servo,RenaudParis/servo,wartman4404/servo,steveklabnik/servo,WriterOfAlicrow/servo,jlegendary/servo,nnethercote/servo,karlito40/servo,fiji-flo/servo,mbrubeck/servo,codemac/servo,hyowon/servo,splav/servo,codemac/servo,tafia/servo,rixrix/servo,tempbottle/servo,WriterOfAlicrow/servo,tafia/servo,rnestler/servo,dhananjay92/servo,caldwell/servo,evilpie/servo,tafia/servo,larsbergstrom/servo,dvberkel/servo,vks/servo,rixrix/servo,nick-thompson/servo,jimberlage/servo,nnethercote/servo,A-deLuna/servo,WriterOfAlicrow/servo,huonw/servo,mbrubeck/servo,indykish/servo,indykish/servo,anthgur/servo,huonw/servo,upsuper/servo,SimonSapin/servo,karlito40/servo,aidanhs/servo,SimonSapin/servo,CJ8664/servo,nrc/servo,pgonda/servo,cbrewster/servo,szeged/servo,indykish/servo,zentner-kyle/servo,bjwbell/servo,jdramani/servo,kindersung/servo,j3parker/servo,evilpie/servo,s142857/servo,mbrubeck/servo,canaltinova/servo,jlegendary/servo,bjwbell/servo,DominoTree/servo,RenaudParis/servo,peterjoel/servo,aidanhs/servo,saratang/servo,dsandeephegde/servo,sadmansk/servo,pyecs/servo,dvberkel/servo,szeged/servo,hyowon/servo,dvberkel/servo,splav/servo,anthgur/servo,j3parker/servo,nnethercote/servo,emilio/servo,codemac/servo,GyrosOfWar/servo,sadmansk/servo,nnethercote/servo,saratang/servo,peterjoel/servo,walac/servo,thiagopnts/servo,samfoo/servo,paulrouget/servo,avadacatavra/servo,mattnenterprise/servo,s142857/servo,wartman4404/servo,saneyuki/servo,DominoTree/servo,saneyuki/servo,anthgur/servo,fiji-flo/servo,rnestler/servo,brendandahl/servo,meh/servo,notriddle/servo,mdibaiee/servo,wpgallih/servo,rnestler/servo,mt2d2/servo,dvberkel/servo,brendandahl/servo,boghison/servo,GyrosOfWar/servo,wpgallih/servo,tempbottle/servo,rixrix/servo,nnethercote/servo,cbrewster/servo,kindersung/servo,mattnenterprise/servo,thiagopnts/servo,aidanhs/servo,jimberlage/servo,avadacatavra/servo,bjwbell/servo,rixrix/servo,cbrewster/servo,larsbergstrom/servo,splav/servo,s142857/servo,meh/servo,ConnorGBrewster/servo,samfoo/servo,jgraham/servo,notriddle/servo,brendandahl/servo,RenaudParis/servo,avadacatavra/servo,dhananjay92/servo,nnethercote/servo,AnthonyBroadCrawford/servo,walac/servo,wartman4404/servo,mattnenterprise/servo,pyfisch/servo,cbrewster/servo,mdibaiee/servo,eddyb/servo,akosel/servo,youprofit/servo,jimberlage/servo,dhananjay92/servo,ryancanhelpyou/servo,larsbergstrom/servo,karlito40/servo,mt2d2/servo,pgonda/servo,larsbergstrom/servo,nerith/servo,indykish/servo,kindersung/servo,dagnir/servo,dagnir/servo,sadmansk/servo,pyecs/servo,jimberlage/servo,GreenRecycleBin/servo,larsbergstrom/servo,peterjoel/servo,zhangjunlei26/servo,mbrubeck/servo,runarberg/servo,tschneidereit/servo,cbrewster/servo,aweinstock314/servo,tschneidereit/servo,runarberg/servo,samfoo/servo,AnthonyBroadCrawford/servo,rnestler/servo,paulrouget/servo,jlegendary/servo,szeged/servo,upsuper/servo,kindersung/servo,splav/servo,GreenRecycleBin/servo,walac/servo,meh/servo,larsbergstrom/servo,evilpie/servo,ryancanhelpyou/servo,walac/servo,saneyuki/servo,dhananjay92/servo,j3parker/servo,nrc/servo,zentner-kyle/servo,evilpie/servo,caldwell/servo,ConnorGBrewster/servo,mt2d2/servo,nrc/servo,caldwell/servo,hyowon/servo,zhangjunlei26/servo,canaltinova/servo,eddyb/servo,szeged/servo,notriddle/servo,RenaudParis/servo,boghison/servo,evilpie/servo,pyfisch/servo,zhangjunlei26/servo,akosel/servo,s142857/servo,DominoTree/servo,ryancanhelpyou/servo,saneyuki/servo,mattnenterprise/servo,SimonSapin/servo,mattnenterprise/servo,wpgallih/servo,tempbottle/servo,evilpie/servo,tschneidereit/servo,tempbottle/servo,jgraham/servo,A-deLuna/servo,CJ8664/servo,jlegendary/servo,pyfisch/servo,saratang/servo,vks/servo,jimberlage/servo,nick-thompson/servo,paulrouget/servo,CJ8664/servo,pyecs/servo,CJ8664/servo,upsuper/servo,aweinstock314/servo,runarberg/servo,canaltinova/servo,mbrubeck/servo,nnethercote/servo,mt2d2/servo,rentongzhang/servo,wpgallih/servo,KiChjang/servo,j3parker/servo,pgonda/servo,youprofit/servo,dsandeephegde/servo,splav/servo,zhangjunlei26/servo,steveklabnik/servo,jimberlage/servo,youprofit/servo,rixrix/servo,notriddle/servo,boghison/servo,jlegendary/servo,tafia/servo,zentner-kyle/servo,mattnenterprise/servo,evilpie/servo,nick-thompson/servo,notriddle/servo,emilio/servo,walac/servo,kindersung/servo,samfoo/servo,anthgur/servo,emilio/servo,tempbottle/servo,indykish/servo,zhangjunlei26/servo,huonw/servo,canaltinova/servo,meh/servo,jdramani/servo,huonw/servo,saneyuki/servo,nick-thompson/servo,zentner-kyle/servo,wartman4404/servo,codemac/servo,bjwbell/servo,mattnenterprise/servo,wpgallih/servo,eddyb/servo,eddyb/servo,deokjinkim/servo,hyowon/servo,mdibaiee/servo,SimonSapin/servo,mbrubeck/servo,upsuper/servo,zhangjunlei26/servo,rentongzhang/servo,huonw/servo,g-k/servo,ryancanhelpyou/servo,jdramani/servo,CJ8664/servo,sadmansk/servo,nnethercote/servo,larsbergstrom/servo,rixrix/servo,A-deLuna/servo,GreenRecycleBin/servo,nrc/servo,jgraham/servo,DominoTree/servo,akosel/servo,rnestler/servo,avadacatavra/servo,vks/servo,avadacatavra/servo,zentner-kyle/servo,pgonda/servo,GyrosOfWar/servo,dati91/servo,thiagopnts/servo,sadmansk/servo,brendandahl/servo,saneyuki/servo,caldwell/servo,rentongzhang/servo,ConnorGBrewster/servo,caldwell/servo,nnethercote/servo,AnthonyBroadCrawford/servo,ryancanhelpyou/servo,saneyuki/servo,jdramani/servo,mdibaiee/servo,vks/servo,wartman4404/servo,splav/servo,deokjinkim/servo,peterjoel/servo,pyecs/servo,wartman4404/servo,fiji-flo/servo,dagnir/servo,mattnenterprise/servo,anthgur/servo,DominoTree/servo,rixrix/servo,evilpie/servo,mdibaiee/servo,fiji-flo/servo,notriddle/servo,splav/servo,walac/servo,j3parker/servo,fiji-flo/servo,dsandeephegde/servo,runarberg/servo,dhananjay92/servo,dvberkel/servo,nnethercote/servo,dati91/servo,deokjinkim/servo,GreenRecycleBin/servo,szeged/servo,codemac/servo,brendandahl/servo,DominoTree/servo,DominoTree/servo,dati91/servo,SimonSapin/servo,SimonSapin/servo,notriddle/servo,mdibaiee/servo,steveklabnik/servo,g-k/servo,AnthonyBroadCrawford/servo,GreenRecycleBin/servo,WriterOfAlicrow/servo,jgraham/servo,steveklabnik/servo,deokjinkim/servo,tafia/servo,mdibaiee/servo,dsandeephegde/servo,saneyuki/servo,dhananjay92/servo,aweinstock314/servo,j3parker/servo,nerith/servo,saratang/servo,indykish/servo,wpgallih/servo,thiagopnts/servo,fiji-flo/servo,caldwell/servo,mt2d2/servo,KiChjang/servo,g-k/servo,akosel/servo,bjwbell/servo,GyrosOfWar/servo,mt2d2/servo,sadmansk/servo,jlegendary/servo,upsuper/servo,meh/servo,nerith/servo,peterjoel/servo,saratang/servo,tempbottle/servo,zhangjunlei26/servo,RenaudParis/servo,g-k/servo,AnthonyBroadCrawford/servo,AnthonyBroadCrawford/servo,jimberlage/servo,nrc/servo,emilio/servo,A-deLuna/servo,rnestler/servo,kindersung/servo,steveklabnik/servo,caldwell/servo,RenaudParis/servo,dagnir/servo,fiji-flo/servo,emilio/servo,boghison/servo,notriddle/servo,cbrewster/servo,bjwbell/servo,aweinstock314/servo,szeged/servo,nerith/servo,WriterOfAlicrow/servo,youprofit/servo,akosel/servo,dagnir/servo,evilpie/servo,kindersung/servo,nerith/servo,pyfisch/servo,indykish/servo,saratang/servo,karlito40/servo,wpgallih/servo,pyecs/servo,dsandeephegde/servo,vks/servo,aidanhs/servo,dvberkel/servo,rentongzhang/servo,zhangjunlei26/servo,hyowon/servo,avadacatavra/servo,paulrouget/servo,eddyb/servo,sadmansk/servo,tschneidereit/servo,thiagopnts/servo,aidanhs/servo,bjwbell/servo,szeged/servo,paulrouget/servo,larsbergstrom/servo,jgraham/servo,szeged/servo,anthgur/servo,GyrosOfWar/servo,s142857/servo,wpgallih/servo,huonw/servo,canaltinova/servo,rentongzhang/servo,boghison/servo,jdramani/servo,KiChjang/servo,aweinstock314/servo,mbrubeck/servo,SimonSapin/servo,dati91/servo,runarberg/servo,dsandeephegde/servo,KiChjang/servo,ryancanhelpyou/servo,deokjinkim/servo,deokjinkim/servo,larsbergstrom/servo,KiChjang/servo,dati91/servo,pyfisch/servo,j3parker/servo,peterjoel/servo,ConnorGBrewster/servo,wpgallih/servo,splav/servo,GyrosOfWar/servo,A-deLuna/servo,nerith/servo,rnestler/servo,paulrouget/servo,splav/servo,dati91/servo,tempbottle/servo,tafia/servo,GyrosOfWar/servo,zentner-kyle/servo,saneyuki/servo,canaltinova/servo,notriddle/servo,dsandeephegde/servo,walac/servo,akosel/servo,canaltinova/servo,eddyb/servo