Auto merge of #23940 - servo:fix-layout-2020, r=emilio
Auto merge of #23940 - servo:fix-layout-2020, r=emilio

Always send epochs to webrender in layout 2020

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