[libclang] Do a AST concurrency check in clang_indexTranslationUnit_Impl.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@164626 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/libclang/Indexing.cpp b/tools/libclang/Indexing.cpp
index 8fe9c36..ae52004 100644
--- a/tools/libclang/Indexing.cpp
+++ b/tools/libclang/Indexing.cpp
@@ -539,6 +539,8 @@
   if (!Unit)
     return;
 
+  ASTUnit::ConcurrencyCheck Check(*Unit);
+
   FileManager &FileMgr = Unit->getFileManager();
 
   if (Unit->getOriginalSourceFileName().empty())