replace entered|leftDocumentCallback support: addresses https://github.com/Polymer/platform/issues/41.
replace entered|leftDocumentCallback support: addresses https://github.com/Polymer/platform/issues/41.

M4gn4tor/polymer,ThiagoGarciaAlves/polymer,jscissr/polymer,bright-sparks/polymer,fjkfwz/polymer,simo97/polymer,codegist/polymer,HiWong/polymer,chimpinano/polymer,MartinsThiago/polymer,jordanyaker/polymer,gazal-k/polymer,MartinsThiago/polymer,tjsavage/polymer,pacificIT/polymer,ikeagold/polymer,akintoey/polymer,jscissr/polymer,mauricionr/polymer,gronke/polymer,mgiuffrida/polymer,JeremybellEU/polymer,henrylee2cn/polymer,MartinMoizard/polymer,ikeagold/polymer,elkamel/polymer,filaraujo/polymer,tekjava/polymer,exlerdesigns/polymer,YOTOV-LIMITED/polymer,MetaMemoryT/polymer,thiagolucio/polymer,gazal-k/polymer,cbmeeks/polymer,tekjava/polymer,Litor/polymer,samccone/polymer,kristianmandrup/polymer,jforge/polymer,BrianLTJ/polymer,cbmeeks/polymer,zxs0827/polymer,mgiuffrida/polymer,gronke/polymer,marcus7777/polymer,kristianmandrup/polymer,ankurvr/polymer,Endika/polymer,Zagorakiss/polymer,cgvarela/polymer,dalong123/polymer,jforge/polymer,itnirmaan/polymer,JsonChiu/polymer,yangjae/polymer,Zagorakiss/polymer,udhayam/polymer,udhayam/polymer,dalong123/polymer,simonfan/polymer,leitzler/polymer,fjkfwz/polymer,Endika/polymer,pacificIT/polymer,henrylee2cn/polymer,BrianLTJ/polymer,chimpinano/polymer,MetaMemoryT/polymer,Polymer/polymer,yangjae/polymer,filaraujo/polymer,itnirmaan/polymer,carbono-io/polymer,codegist/polymer,HiWong/polymer,jvkops/polymer,samccone/polymer,simonfan/polymer,mgiuffrida/polymer,udhayam/polymer,jpalomar/polymer,Tudes/polymer,simo97/polymer,vic/polymer,zebMcCorkle/polymer,Tudes/polymer,Endika/polymer,ktiedt/polymer,jvkops/polymer,simonfan/polymer,jpalomar/polymer,sekiyaeiji/polymer,brandonmowat/polymer,elkamel/polymer,simonsoft/polymer,jordanyaker/polymer,tachyon1337/polymer,ktiedt/polymer,HiWong/polymer,jpalomar/polymer,ktiedt/polymer,TedaLIEz/polymer,ilovezy/polymer,simonsoft/polymer,yforrest/polymer,filaraujo/polymer,paulballesty/polymer,marcus7777/polymer,Flip120/polymer,ikeagold/polymer,paulballesty/polymer,jordanyaker/polymer,JsonChiu/polymer,samccone/polymer,rafaelducati/polymer,elkamel/polymer,thiagolucio/polymer,gazal-k/polymer,yforrest/polymer,Flip120/polymer,YOTOV-LIMITED/polymer,fjkfwz/polymer,rafaelducati/polymer,jvkops/polymer,kristianmandrup/polymer,Tudes/polymer,Kabele/polymer,japacible/polymer,zebMcCorkle/polymer,japacible/polymer,zxs0827/polymer,JeremybellEU/polymer,vic/polymer,cgvarela/polymer,cbmeeks/polymer,tachyon1337/polymer,brandonmowat/polymer,dotDeeka/polymer,M4gn4tor/polymer,studiowangfei/polymer,ilovezy/polymer,carbono-io/polymer,zxs0827/polymer,youprofit/polymer,chimpinano/polymer,bright-sparks/polymer,Polymer/polymer,dotDeeka/polymer,MartinMoizard/polymer,sekiyaeiji/polymer,tjsavage/polymer,cgvarela/polymer,simo97/polymer,exlerdesigns/polymer,JeremybellEU/polymer,exlerdesigns/polymer,henrylee2cn/polymer,gronke/polymer,pacificIT/polymer,ThiagoGarciaAlves/polymer,thiagolucio/polymer,studiowangfei/polymer,leitzler/polymer,YOTOV-LIMITED/polymer,akintoey/polymer,Kabele/polymer,jscissr/polymer,Litor/polymer,dalong123/polymer,MartinMoizard/polymer,Litor/polymer,yforrest/polymer,MartinsThiago/polymer,bright-sparks/polymer,akintoey/polymer,tekjava/polymer,tjsavage/polymer,itnirmaan/polymer,BrianLTJ/polymer,TedaLIEz/polymer,Polymer/polymer,youprofit/polymer,carbono-io/polymer,ankurvr/polymer,mauricionr/polymer