[AST] Convert MangleNumberingContext to a unique_ptr.

Summary: It doesn't need to be refcounted anymore, either.

Reviewers: timshen

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D25420

llvm-svn: 283768
diff --git a/clang/lib/AST/ItaniumCXXABI.cpp b/clang/lib/AST/ItaniumCXXABI.cpp
index 8a2cc0f..482c3c5 100644
--- a/clang/lib/AST/ItaniumCXXABI.cpp
+++ b/clang/lib/AST/ItaniumCXXABI.cpp
@@ -163,8 +163,9 @@
     return nullptr;
   }
 
-  MangleNumberingContext *createMangleNumberingContext() const override {
-    return new ItaniumNumberingContext();
+  std::unique_ptr<MangleNumberingContext>
+  createMangleNumberingContext() const override {
+    return llvm::make_unique<ItaniumNumberingContext>();
   }
 };
 }