Document the use and meaning of the devtools control messages. Fixes #6922.
Document the use and meaning of the devtools control messages. Fixes #6922.

DominoTree/servo,notriddle/servo,nnethercote/servo,KiChjang/servo,GyrosOfWar/servo,paulrouget/servo,thiagopnts/servo,runarberg/servo,cbrewster/servo,dati91/servo,CJ8664/servo,pyfisch/servo,dsandeephegde/servo,steveklabnik/servo,anthgur/servo,akosel/servo,upsuper/servo,paulrouget/servo,mbrubeck/servo,walac/servo,CJ8664/servo,avadacatavra/servo,aidanhs/servo,nrc/servo,dvberkel/servo,fiji-flo/servo,aidanhs/servo,sadmansk/servo,rnestler/servo,splav/servo,mdibaiee/servo,larsbergstrom/servo,SimonSapin/servo,WriterOfAlicrow/servo,cbrewster/servo,runarberg/servo,saneyuki/servo,rentongzhang/servo,tafia/servo,anthgur/servo,bjwbell/servo,szeged/servo,upsuper/servo,larsbergstrom/servo,anthgur/servo,dagnir/servo,KiChjang/servo,dhananjay92/servo,youprofit/servo,upsuper/servo,meh/servo,emilio/servo,jdramani/servo,eddyb/servo,upsuper/servo,wartman4404/servo,dati91/servo,sadmansk/servo,kindersung/servo,nrc/servo,KiChjang/servo,jdramani/servo,akosel/servo,aidanhs/servo,KiChjang/servo,walac/servo,runarberg/servo,wartman4404/servo,youprofit/servo,DominoTree/servo,saratang/servo,brendandahl/servo,RenaudParis/servo,akosel/servo,fiji-flo/servo,RenaudParis/servo,rnestler/servo,steveklabnik/servo,rentongzhang/servo,cbrewster/servo,vks/servo,eddyb/servo,jlegendary/servo,mdibaiee/servo,rentongzhang/servo,splav/servo,saneyuki/servo,akosel/servo,nrc/servo,splav/servo,peterjoel/servo,j3parker/servo,kindersung/servo,dsandeephegde/servo,ConnorGBrewster/servo,dvberkel/servo,sadmansk/servo,pyfisch/servo,meh/servo,peterjoel/servo,pyfisch/servo,nnethercote/servo,dsandeephegde/servo,saneyuki/servo,wartman4404/servo,avadacatavra/servo,mbrubeck/servo,cbrewster/servo,A-deLuna/servo,ConnorGBrewster/servo,CJ8664/servo,dati91/servo,rentongzhang/servo,saneyuki/servo,pyfisch/servo,emilio/servo,szeged/servo,brendandahl/servo,mattnenterprise/servo,peterjoel/servo,mdibaiee/servo,huonw/servo,pyfisch/servo,dagnir/servo,fiji-flo/servo,AnthonyBroadCrawford/servo,wartman4404/servo,szeged/servo,DominoTree/servo,mattnenterprise/servo,saneyuki/servo,rnestler/servo,codemac/servo,caldwell/servo,fiji-flo/servo,AnthonyBroadCrawford/servo,runarberg/servo,mbrubeck/servo,mbrubeck/servo,larsbergstrom/servo,AnthonyBroadCrawford/servo,nrc/servo,wartman4404/servo,tafia/servo,dhananjay92/servo,tafia/servo,kindersung/servo,canaltinova/servo,sadmansk/servo,RenaudParis/servo,mattnenterprise/servo,larsbergstrom/servo,j3parker/servo,mattnenterprise/servo,dagnir/servo,jimberlage/servo,codemac/servo,jlegendary/servo,upsuper/servo,bjwbell/servo,pyfisch/servo,szeged/servo,anthgur/servo,avadacatavra/servo,huonw/servo,nnethercote/servo,tafia/servo,ConnorGBrewster/servo,sadmansk/servo,brendandahl/servo,thiagopnts/servo,notriddle/servo,emilio/servo,steveklabnik/servo,jdramani/servo,emilio/servo,jimberlage/servo,youprofit/servo,larsbergstrom/servo,CJ8664/servo,emilio/servo,SimonSapin/servo,ConnorGBrewster/servo,upsuper/servo,anthgur/servo,mbrubeck/servo,jimberlage/servo,eddyb/servo,GyrosOfWar/servo,bjwbell/servo,dsandeephegde/servo,steveklabnik/servo,steveklabnik/servo,rnestler/servo,saneyuki/servo,akosel/servo,jimberlage/servo,SimonSapin/servo,jdramani/servo,avadacatavra/servo,splav/servo,rnestler/servo,KiChjang/servo,thiagopnts/servo,saratang/servo,eddyb/servo,dvberkel/servo,paulrouget/servo,avadacatavra/servo,cbrewster/servo,AnthonyBroadCrawford/servo,avadacatavra/servo,RenaudParis/servo,SimonSapin/servo,caldwell/servo,j3parker/servo,aidanhs/servo,saratang/servo,szeged/servo,cbrewster/servo,peterjoel/servo,meh/servo,j3parker/servo,notriddle/servo,splav/servo,akosel/servo,canaltinova/servo,vks/servo,walac/servo,brendandahl/servo,j3parker/servo,saratang/servo,nnethercote/servo,DominoTree/servo,splav/servo,jimberlage/servo,dagnir/servo,larsbergstrom/servo,DominoTree/servo,aidanhs/servo,notriddle/servo,CJ8664/servo,dagnir/servo,huonw/servo,larsbergstrom/servo,mattnenterprise/servo,huonw/servo,SimonSapin/servo,A-deLuna/servo,DominoTree/servo,bjwbell/servo,saneyuki/servo,caldwell/servo,szeged/servo,notriddle/servo,eddyb/servo,jdramani/servo,vks/servo,pyfisch/servo,emilio/servo,meh/servo,upsuper/servo,szeged/servo,pyfisch/servo,dsandeephegde/servo,RenaudParis/servo,tafia/servo,sadmansk/servo,GyrosOfWar/servo,caldwell/servo,mbrubeck/servo,mdibaiee/servo,jimberlage/servo,larsbergstrom/servo,szeged/servo,meh/servo,KiChjang/servo,notriddle/servo,meh/servo,saneyuki/servo,codemac/servo,youprofit/servo,saratang/servo,nnethercote/servo,fiji-flo/servo,CJ8664/servo,notriddle/servo,notriddle/servo,rnestler/servo,peterjoel/servo,codemac/servo,saneyuki/servo,A-deLuna/servo,CJ8664/servo,huonw/servo,caldwell/servo,jlegendary/servo,KiChjang/servo,brendandahl/servo,eddyb/servo,upsuper/servo,peterjoel/servo,anthgur/servo,thiagopnts/servo,paulrouget/servo,dagnir/servo,eddyb/servo,splav/servo,anthgur/servo,jimberlage/servo,saratang/servo,larsbergstrom/servo,DominoTree/servo,dvberkel/servo,nnethercote/servo,kindersung/servo,cbrewster/servo,vks/servo,caldwell/servo,dati91/servo,GyrosOfWar/servo,WriterOfAlicrow/servo,mdibaiee/servo,splav/servo,mdibaiee/servo,thiagopnts/servo,dhananjay92/servo,cbrewster/servo,youprofit/servo,A-deLuna/servo,codemac/servo,mdibaiee/servo,szeged/servo,caldwell/servo,RenaudParis/servo,jdramani/servo,rnestler/servo,ConnorGBrewster/servo,jlegendary/servo,paulrouget/servo,rentongzhang/servo,pyfisch/servo,WriterOfAlicrow/servo,WriterOfAlicrow/servo,kindersung/servo,youprofit/servo,nnethercote/servo,jlegendary/servo,notriddle/servo,akosel/servo,runarberg/servo,tafia/servo,mattnenterprise/servo,SimonSapin/servo,aidanhs/servo,ConnorGBrewster/servo,runarberg/servo,ConnorGBrewster/servo,tafia/servo,canaltinova/servo,eddyb/servo,nrc/servo,splav/servo,dsandeephegde/servo,avadacatavra/servo,meh/servo,WriterOfAlicrow/servo,AnthonyBroadCrawford/servo,GyrosOfWar/servo,rentongzhang/servo,peterjoel/servo,larsbergstrom/servo,dvberkel/servo,dati91/servo,kindersung/servo,KiChjang/servo,thiagopnts/servo,GyrosOfWar/servo,anthgur/servo,jimberlage/servo,avadacatavra/servo,AnthonyBroadCrawford/servo,walac/servo,canaltinova/servo,j3parker/servo,A-deLuna/servo,paulrouget/servo,A-deLuna/servo,dsandeephegde/servo,pyfisch/servo,dsandeephegde/servo,dvberkel/servo,nnethercote/servo,rnestler/servo,emilio/servo,nnethercote/servo,fiji-flo/servo,mbrubeck/servo,dati91/servo,paulrouget/servo,fiji-flo/servo,dati91/servo,vks/servo,vks/servo,j3parker/servo,kindersung/servo,nrc/servo,WriterOfAlicrow/servo,paulrouget/servo,wartman4404/servo,saratang/servo,walac/servo,fiji-flo/servo,ConnorGBrewster/servo,SimonSapin/servo,codemac/servo,mbrubeck/servo,DominoTree/servo,canaltinova/servo,brendandahl/servo,jdramani/servo,nrc/servo,steveklabnik/servo,splav/servo,mattnenterprise/servo,runarberg/servo,bjwbell/servo,sadmansk/servo,canaltinova/servo,CJ8664/servo,peterjoel/servo,rentongzhang/servo,WriterOfAlicrow/servo,codemac/servo,canaltinova/servo,paulrouget/servo,steveklabnik/servo,huonw/servo,DominoTree/servo,GyrosOfWar/servo,thiagopnts/servo,bjwbell/servo,dagnir/servo,bjwbell/servo,paulrouget/servo,jlegendary/servo,dhananjay92/servo,sadmansk/servo,wartman4404/servo,thiagopnts/servo,peterjoel/servo,RenaudParis/servo,notriddle/servo,huonw/servo,saneyuki/servo,KiChjang/servo,emilio/servo,SimonSapin/servo,youprofit/servo,KiChjang/servo,dhananjay92/servo,aidanhs/servo,emilio/servo,jimberlage/servo,canaltinova/servo,dvberkel/servo,walac/servo,szeged/servo,peterjoel/servo,DominoTree/servo,nnethercote/servo,A-deLuna/servo,dati91/servo,dhananjay92/servo,vks/servo,emilio/servo,jlegendary/servo,dhananjay92/servo,AnthonyBroadCrawford/servo,mattnenterprise/servo,brendandahl/servo,walac/servo