shorten the definition of BackgroundCompleter
shorten the definition of BackgroundCompleter

borgified/vimium,douglas-larocca/vimium,jb55/vimium-plus,smblott-github/vimium-smblott,tuchangwei/vimium,justalittlenoob/vimium,willsALMANJ/vimium,elderbas/vimium,poacher2k/vimium,gdh1995/vimium,wildeyes/vimium,elegantwww/vimium,smblott-github/vimium,Aleroniponi/vimium,crazypenguincode/vimium,PrestanceDesign/vimium,PickRelated/vimium,zhangmin510/vimium,VPashkov/vimium,Aleroniponi/vimium,elegantwww/vimium,mrmr1993/vimium,decaffeinate-examples/vimium,PickRelated/vimium,decaffeinate-examples/vimium,gdh1995/vimium,elderbas/vimium,csmalin/vimium,borgified/vimium,VPashkov/vimium,csmalin/vimium,Aleroniponi/vimium,jb55/vimium-plus,dimatter/vimium,philc/vimium,wildeyes/vimium,philc/vimium,cyrixhero/vimium,justalittlenoob/vimium,wildeyes/vimium,hhsue/vimium,PrestanceDesign/vimium,philc/vimium,shaung/vimium,mrmr1993/vimium,elegantwww/vimium,douglas-larocca/vimium,bkudria/vimium,cyrixhero/vimium,elderbas/vimium,justalittlenoob/vimium,willsALMANJ/vimium,hhsue/vimium,cyrixhero/vimium,poacher2k/vimium,borgified/vimium,Lw-Cui/vimium,gdh1995/vimium,Robinson10240/vimium,Robinson10240/vimium,tuchangwei/vimium,smblott-github/vimium,hhsue/vimium,douglas-larocca/vimium,dimatter/vimium,VPashkov/vimium,crazypenguincode/vimium,Robinson10240/vimium,decaffeinate-examples/vimium,Lw-Cui/vimium,zhangmin510/vimium,bkudria/vimium,Lw-Cui/vimium,willsALMANJ/vimium,bkudria/vimium,smblott-github/vimium-smblott,zhangmin510/vimium,tuchangwei/vimium,dimatter/vimium,poacher2k/vimium,smblott-github/vimium,mrmr1993/vimium,csmalin/vimium,PickRelated/vimium,PrestanceDesign/vimium