Use forward declaration instead of #include.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176770 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unneeded const_cast.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176771 91177308-0d34-0410-b5e6-96231b3b80d8
Test case hygiene.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176772 91177308-0d34-0410-b5e6-96231b3b80d8
Fix test case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176773 91177308-0d34-0410-b5e6-96231b3b80d8