Add missing include and qualify StringRef.
Add missing include and qualify StringRef.

olifre/root,olifre/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root