Constify a few functions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185520 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused field.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185523 91177308-0d34-0410-b5e6-96231b3b80d8