Auto merge of #11408 - Ms2ger:layoutthread-url, r=Manishearth
Auto merge of #11408 - Ms2ger:layoutthread-url, r=Manishearth

Take LayoutThread::url out of its RefCell.

Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data:
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy --faster` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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