[libclang] Do a AST concurrency check in clang_indexTranslationUnit_Impl.

llvm-svn: 164626
diff --git a/clang/tools/libclang/Indexing.cpp b/clang/tools/libclang/Indexing.cpp
index 8fe9c36..ae52004 100644
--- a/clang/tools/libclang/Indexing.cpp
+++ b/clang/tools/libclang/Indexing.cpp
@@ -539,6 +539,8 @@
   if (!Unit)
     return;
 
+  ASTUnit::ConcurrencyCheck Check(*Unit);
+
   FileManager &FileMgr = Unit->getFileManager();
 
   if (Unit->getOriginalSourceFileName().empty())