Use StringRefMemoryObject. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221502 91177308-0d34-0410-b5e6-96231b3b80d8
Use a StringRefMemoryObject. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221503 91177308-0d34-0410-b5e6-96231b3b80d8