style: Add parsing of the loose|normal|strict values of the CSS line-break property.
style: Add parsing of the loose|normal|strict values of the CSS line-break property.

Differential Revision: https://phabricator.services.mozilla.com/D30785

KiChjang/servo,pyfisch/servo,splav/servo,nnethercote/servo,notriddle/servo,DominoTree/servo,KiChjang/servo,KiChjang/servo,pyfisch/servo,paulrouget/servo,larsbergstrom/servo,nnethercote/servo,splav/servo,pyfisch/servo,splav/servo,saneyuki/servo,paulrouget/servo,pyfisch/servo,emilio/servo,DominoTree/servo,DominoTree/servo,nnethercote/servo,KiChjang/servo,larsbergstrom/servo,saneyuki/servo,DominoTree/servo,splav/servo,notriddle/servo,pyfisch/servo,DominoTree/servo,saneyuki/servo,emilio/servo,paulrouget/servo,splav/servo,saneyuki/servo,paulrouget/servo,saneyuki/servo,notriddle/servo,KiChjang/servo,larsbergstrom/servo,splav/servo,splav/servo,DominoTree/servo,nnethercote/servo,saneyuki/servo,DominoTree/servo,KiChjang/servo,nnethercote/servo,KiChjang/servo,KiChjang/servo,paulrouget/servo,notriddle/servo,larsbergstrom/servo,notriddle/servo,pyfisch/servo,emilio/servo,larsbergstrom/servo,larsbergstrom/servo,pyfisch/servo,larsbergstrom/servo,pyfisch/servo,saneyuki/servo,nnethercote/servo,DominoTree/servo,notriddle/servo,larsbergstrom/servo,splav/servo,emilio/servo,emilio/servo,saneyuki/servo,paulrouget/servo,larsbergstrom/servo,pyfisch/servo,nnethercote/servo,paulrouget/servo,DominoTree/servo,larsbergstrom/servo,emilio/servo,KiChjang/servo,paulrouget/servo,notriddle/servo,splav/servo,emilio/servo,nnethercote/servo,paulrouget/servo,emilio/servo,notriddle/servo,emilio/servo,emilio/servo,saneyuki/servo,notriddle/servo,saneyuki/servo,pyfisch/servo,KiChjang/servo,splav/servo,DominoTree/servo,notriddle/servo,nnethercote/servo,nnethercote/servo,paulrouget/servo