Silence unused variable warning in non-assert builds.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187572 91177308-0d34-0410-b5e6-96231b3b80d8
Make helper function static.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@187574 91177308-0d34-0410-b5e6-96231b3b80d8