Auto merge of #16643 - glennw:update-wr-bits-and-pieces, r=jdm
Auto merge of #16643 - glennw:update-wr-bits-and-pieces, r=jdm

Update WR (various bits and pieces).

* Split out positioning and clipping per display item.
* Only send scroll states for clips that actually scroll.
* NV12 texture format support.
* Make dithering a feature.
* Handle radial gradients with invalid radii.

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