Remove unused field.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@182874 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 946d3df..c1f3152 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -716,8 +716,7 @@
     ExternalSource(0), Listener(0),
     Comments(SM), CommentsLoaded(false),
     CommentCommandTraits(BumpAlloc, LOpts.CommentOpts),
-    LastSDM(0, 0),
-    UniqueBlockByRefTypeID(0)
+    LastSDM(0, 0)
 {
   if (size_reserve > 0) Types.reserve(size_reserve);
   TUDecl = TranslationUnitDecl::Create(*this);