Revert r325321 "[Sema] Take into account the current context when checking the"

This broke the Chromium build, see https://crbug.com/813017

> accessibility of a class member.
>
> This fixes PR32898.
>
> rdar://problem/33737747
>
> Differential revision: https://reviews.llvm.org/D36918

llvm-svn: 325335