[GraphWriter] Change GraphWriter to use NodeRef in GraphTraits

Summary: Corresponding LLVM patch: D23580

Reviewers: dblaikie

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D23581

llvm-svn: 278963

clang/lib/Serialization/ModuleManager.cpp

@@ -434,6 +434,7 @@ namespace llvm {
   template<>
   struct GraphTraits<ModuleManager> {
     typedef ModuleFile NodeType;
+    typedef ModuleFile *NodeRef;
     typedef llvm::SetVector<ModuleFile *>::const_iterator ChildIteratorType;
     typedef ModuleManager::ModuleConstIterator nodes_iterator;