Fix: CSSOM constructors should be available on the DOM.
Fix: CSSOM constructors should be available on the DOM.

level2/style.js adds properties to the level2 core instance, so it
shouldn't operate on a cloned version.

nicolashenry/jsdom,Sebmaster/jsdom,evdevgit/jsdom,jeffcarp/jsdom,papandreou/jsdom,cpojer/jsdom,sirbrillig/jsdom,kesla/jsdom,crealogix/jsdom,Sebmaster/jsdom,selam/jsdom,lcstore/jsdom,darobin/jsdom,janusnic/jsdom,jeffcarp/jsdom,aduyng/jsdom,medikoo/jsdom,vestineo/jsdom,jeffcarp/jsdom,isaacs/jsdom,kittens/jsdom,susaing/jsdom,nicolashenry/jsdom,kesla/jsdom,fiftin/jsdom,janusnic/jsdom,godmar/jsdom,Sebmaster/jsdom,Ye-Yong-Chi/jsdom,crealogix/jsdom,danieljoppi/jsdom,AshCoolman/jsdom,fiftin/jsdom,sirbrillig/jsdom,Joris-van-der-Wel/jsdom,papandreou/jsdom,nicolashenry/jsdom,mzgol/jsdom,brianmcd/cloudbrowser-jsdom,szarouski/jsdom,mbostock/jsdom,dexteryy/jsdom-nogyp,kangax/jsdom,concord-consortium/jsdom,concord-consortium/jsdom,robertknight/jsdom,kevinold/jsdom,tmpvar/jsdom,medikoo/jsdom,lcstore/jsdom,susaing/jsdom,sebmck/jsdom,evanlucas/jsdom,zaucy/jsdom,Zirro/jsdom,robertknight/jsdom,susaing/jsdom,beni55/jsdom,darobin/jsdom,robertknight/jsdom,snuggs/jsdom,Ye-Yong-Chi/jsdom,tmpvar/jsdom,kittens/jsdom,fiftin/jsdom,evanlucas/jsdom,mbostock/jsdom,cpojer/jsdom,AshCoolman/jsdom,mbostock/jsdom,isaacs/jsdom,danieljoppi/jsdom,sebmck/jsdom,beni55/jsdom,kevinold/jsdom,Ye-Yong-Chi/jsdom,Zirro/jsdom,medikoo/jsdom,vestineo/jsdom,lcstore/jsdom,iizukanao/jsdom,szarouski/jsdom,danieljoppi/jsdom,selam/jsdom,janusnic/jsdom,brianmcd/cloudbrowser-jsdom,iizukanao/jsdom,zaucy/jsdom,selam/jsdom,aduyng/jsdom,kittens/jsdom,AshCoolman/jsdom,beni55/jsdom,Joris-van-der-Wel/jsdom,sebmck/jsdom,zaucy/jsdom,kesla/jsdom,Joris-van-der-Wel/jsdom,darobin/jsdom,mzgol/jsdom,dexteryy/jsdom-nogyp,kangax/jsdom,cpojer/jsdom,evdevgit/jsdom,mzgol/jsdom,AVGP/jsdom,szarouski/jsdom,AVGP/jsdom,snuggs/jsdom,evanlucas/jsdom,evdevgit/jsdom,godmar/jsdom,sirbrillig/jsdom,aduyng/jsdom,kevinold/jsdom,vestineo/jsdom