[CodeComplete] Re-fix accessibilty of protected members from base class.

Summary:
The initial fix (r337453) had bug and was partially reverted (r338255).
This simplies the original fix by explicitly passing the naming class to the
completion consumer.

Reviewers: ilya-biryukov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D52647

llvm-svn: 343575