Make ChainedIncludesSource an ExternalSemaSource, otherwise initialization of the ASTReader is incomplete, leading to errors like not realizing std::type_info is already defined.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@128664 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Serialization/ChainedIncludesSource.cpp b/lib/Serialization/ChainedIncludesSource.cpp
index aba1eae3..4b95419 100644
--- a/lib/Serialization/ChainedIncludesSource.cpp
+++ b/lib/Serialization/ChainedIncludesSource.cpp
@@ -208,3 +208,18 @@
 void ChainedIncludesSource::PrintStats() {
   return getFinalReader().PrintStats();
 }
+
+void ChainedIncludesSource::InitializeSema(Sema &S) {
+  return getFinalReader().InitializeSema(S);
+}
+void ChainedIncludesSource::ForgetSema() {
+  return getFinalReader().ForgetSema();
+}
+std::pair<ObjCMethodList,ObjCMethodList>
+ChainedIncludesSource::ReadMethodPool(Selector Sel) {
+  return getFinalReader().ReadMethodPool(Sel);
+}
+bool ChainedIncludesSource::LookupUnqualified(LookupResult &R, Scope *S) {
+  return getFinalReader().LookupUnqualified(R, S);
+}
+