return pre-built lists. Instead, it feeds the methods it deserializes
to Sema so that Sema can unique them, which keeps the chains shorter.
llvm-svn: 148889
belonged in the Serialization library, it's setting up a compilation,
not just deserializing.
This should fix PR11512, making Serialization actually be layered below
Frontend, a long standing layering violation in Clang.
llvm-svn: 146233