[C++11] Add 'override' keyword to virtual methods that override their base class.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203220 91177308-0d34-0410-b5e6-96231b3b80d8
Remove unused method.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203221 91177308-0d34-0410-b5e6-96231b3b80d8