(Wangle) Optimize empty continuation
(Wangle) Optimize empty continuation

Summary: It should remove one malloc as per the task.

Test Plan: `fbconfig folly/wangle && fbmake runtests` Also, `--clang`.

Reviewed By: davejwatson@fb.com

Subscribers: fugalh

FB internal diff: D1498331

Tasks: 4913277

SammyK/folly,CJstar/folly,mqeizi/folly,gavioto/folly,ykarlsbrun/folly,romange/folly,CJstar/folly,clearlylin/folly,reddit/folly,kernelim/folly,renyinew/folly,stonegithubs/folly,alexst07/folly,tempbottle/folly,alexst07/folly,bsampath/folly,guker/folly,floxard/folly,zhiweicai/folly,yangjin-unique/folly,xzmagic/folly,gavioto/folly,kernelim/folly,nickhen/folly,bobegir/folly,tomhughes/folly,tomhughes/folly,yangjin-unique/folly,cppfool/folly,Orvid/folly,bowlofstew/folly,cole14/folly,chjp2046/folly,loverszhaokai/folly,juniway/folly,wildinto/folly,ykarlsbrun/folly,fw1121/folly,rklabs/folly,fw1121/folly,bobegir/folly,reddit/folly,guker/folly,raphaelamorim/folly,juniway/folly,colemancda/folly,chjp2046/folly,arg0/folly,loversInJapan/folly,gaoyingie/folly,tempbottle/folly,reddit/folly,reddit/folly,PPC64/folly,bsampath/folly,cppfool/folly,PoisonBOx/folly,renyinew/folly,bobegir/folly,brunomorishita/folly,raphaelamorim/folly,SeanRBurton/folly,leolujuyi/folly,juniway/folly,sonnyhu/folly,CJstar/folly,SeanRBurton/folly,bsampath/folly,hongliangzhao/folly,Eagle-X/folly,loversInJapan/folly,PPC64/folly,Eagle-X/folly,Orvid/folly,PoisonBOx/folly,hongliangzhao/folly,leolujuyi/folly,floxard/folly,cppfool/folly,arg0/folly,facebook/folly,sonnyhu/folly,bikong2/folly,Hincoin/folly,cole14/folly,Hincoin/folly,lifei/folly,raphaelamorim/folly,Orvid/folly,romange/folly,loversInJapan/folly,charsyam/folly,chjp2046/folly,PPC64/folly,KSreeHarsha/folly,bsampath/folly,Eagle-X/folly,bowlofstew/folly,zhiweicai/folly,facebook/folly,KSreeHarsha/folly,facebook/folly,mqeizi/folly,bikong2/folly,gavioto/folly,renyinew/folly,clearlinux/folly,project-zerus/folly,bowlofstew/folly,shaobz/folly,gaoyingie/folly,sonnyhu/folly,colemancda/folly,CJstar/folly,bobegir/folly,guker/folly,fw1121/folly,zhiweicai/folly,upsoft/folly,theiver9827/folly,raphaelamorim/folly,nickhen/folly,alexst07/folly,KSreeHarsha/folly,floxard/folly,xzmagic/folly,zhiweicai/folly,Orvid/folly,colemancda/folly,constantine001/folly,shaobz/folly,theiver9827/folly,PoisonBOx/folly,xzmagic/folly,constantine001/folly,guker/folly,KSreeHarsha/folly,renyinew/folly,PPC64/folly,bowlofstew/folly,tempbottle/folly,upsoft/folly,sonnyhu/folly,KSreeHarsha/folly,loversInJapan/folly,doctaweeks/folly,gaoyingie/folly,mqeizi/folly,xzmagic/folly,doctaweeks/folly,lifei/folly,cppfool/folly,upsoft/folly,zhiweicai/folly,stonegithubs/folly,clearlinux/folly,romange/folly,cppfool/folly,nickhen/folly,doctaweeks/folly,juniway/folly,brunomorishita/folly,shaobz/folly,Hincoin/folly,Eagle-X/folly,chjp2046/folly,bikong2/folly,rklabs/folly,SammyK/folly,tomhughes/folly,Hincoin/folly,project-zerus/folly,clearlinux/folly,hongliangzhao/folly,lifei/folly,cole14/folly,floxard/folly,doctaweeks/folly,constantine001/folly,theiver9827/folly,sonnyhu/folly,clearlylin/folly,arg0/folly,colemancda/folly,bowlofstew/folly,clearlylin/folly,clearlylin/folly,bikong2/folly,hongliangzhao/folly,lifei/folly,PoisonBOx/folly,alexst07/folly,project-zerus/folly,floxard/folly,romange/folly,loverszhaokai/folly,SammyK/folly,rklabs/folly,clearlylin/folly,tempbottle/folly,stonegithubs/folly,nickhen/folly,rklabs/folly,kernelim/folly,renyinew/folly,gaoyingie/folly,arg0/folly,SeanRBurton/folly,sakishum/folly,loverszhaokai/folly,ykarlsbrun/folly,upsoft/folly,kernelim/folly,charsyam/folly,cole14/folly,yangjin-unique/folly,theiver9827/folly,PoisonBOx/folly,SammyK/folly,charsyam/folly,tempbottle/folly,fw1121/folly,xzmagic/folly,chjp2046/folly,facebook/folly,stonegithubs/folly,doctaweeks/folly,constantine001/folly,sakishum/folly,mqeizi/folly,ykarlsbrun/folly,bikong2/folly,project-zerus/folly,SammyK/folly,sakishum/folly,bsampath/folly,nickhen/folly,SeanRBurton/folly,theiver9827/folly,leolujuyi/folly,gavioto/folly,sakishum/folly,mqeizi/folly,leolujuyi/folly,ykarlsbrun/folly,stonegithubs/folly,PPC64/folly,charsyam/folly,alexst07/folly,yangjin-unique/folly,romange/folly,Orvid/folly,guker/folly,bobegir/folly,tomhughes/folly,Hincoin/folly,raphaelamorim/folly,loverszhaokai/folly,clearlinux/folly,brunomorishita/folly,tomhughes/folly,hongliangzhao/folly,gavioto/folly,facebook/folly,SeanRBurton/folly,yangjin-unique/folly,sakishum/folly,juniway/folly,shaobz/folly,fw1121/folly,wildinto/folly,shaobz/folly,constantine001/folly,leolujuyi/folly,loverszhaokai/folly,reddit/folly,CJstar/folly,lifei/folly,arg0/folly,wildinto/folly,wildinto/folly,Eagle-X/folly,brunomorishita/folly,kernelim/folly,brunomorishita/folly,gaoyingie/folly,project-zerus/folly,loversInJapan/folly,wildinto/folly,cole14/folly,colemancda/folly,clearlinux/folly,rklabs/folly,upsoft/folly