fix clang build breakage
fix clang build breakage

Summary: ^

Test Plan: compiled.  What a concept.

Reviewed By: woo@fb.com

Subscribers: doug, bmatheny, mathieubaudet

FB internal diff: D1756489

Signature: t1:1756489:1419369051:87194d17f843b3f71f5aa1dda85a2e141fe07b1a

hnutank163/proxygen,fqihangf/proxygen,wrmsr/proxygen,LilMeyer/proxygen,Werror/proxygen,zhenglaizhang/proxygen,hongliangzhao/proxygen,zhenglaizhang/proxygen,zhiweicai/proxygen,LilMeyer/proxygen,Orvid/proxygen,raphaelamorim/proxygen,Werror/proxygen,Orvid/proxygen,luxuan/proxygen,hongliangzhao/proxygen,wrmsr/proxygen,hnutank163/proxygen,raphaelamorim/proxygen,hongliangzhao/proxygen,hongliangzhao/proxygen,pueril/proxygen,jgli/proxygen,supriyantomaftuh/proxygen,chjp2046/proxygen,sssemil/proxygen,songfj/proxygen,supriyantomaftuh/proxygen,wrmsr/proxygen,fqihangf/proxygen,chenmoshushi/proxygen,hnutank163/proxygen,seem-sky/proxygen,chjp2046/proxygen,fqihangf/proxygen,songfj/proxygen,pueril/proxygen,jgli/proxygen,supriyantomaftuh/proxygen,LilMeyer/proxygen,songfj/proxygen,hiproz/proxygen,jgli/proxygen,Orvid/proxygen,chenmoshushi/proxygen,seem-sky/proxygen,pueril/proxygen,raphaelamorim/proxygen,chenmoshushi/proxygen,zhiweicai/proxygen,chjp2046/proxygen,chenmoshushi/proxygen,zhiweicai/proxygen,zhenglaizhang/proxygen,seem-sky/proxygen,raphaelamorim/proxygen,pueril/proxygen,sssemil/proxygen,KublaikhanGeek/proxygen,chjp2046/proxygen,Werror/proxygen,hiproz/proxygen,sssemil/proxygen,seem-sky/proxygen,KublaikhanGeek/proxygen,sssemil/proxygen,luxuan/proxygen,hnutank163/proxygen,Werror/proxygen,songfj/proxygen,zhenglaizhang/proxygen,hiproz/proxygen,wrmsr/proxygen,fqihangf/proxygen,LilMeyer/proxygen,zhiweicai/proxygen,jgli/proxygen,KublaikhanGeek/proxygen,Orvid/proxygen,hiproz/proxygen,luxuan/proxygen,KublaikhanGeek/proxygen,supriyantomaftuh/proxygen