Use std::unique_ptr to make the ownership explicit.

llvm-svn: 214377
diff --git a/llvm/lib/Object/COFFObjectFile.cpp b/llvm/lib/Object/COFFObjectFile.cpp
index 46ef87d..5ba3b78 100644
--- a/llvm/lib/Object/COFFObjectFile.cpp
+++ b/llvm/lib/Object/COFFObjectFile.cpp
@@ -1112,12 +1112,12 @@
   return object_error::success;
 }
 
-ErrorOr<ObjectFile *>
+ErrorOr<std::unique_ptr<COFFObjectFile>>
 ObjectFile::createCOFFObjectFile(std::unique_ptr<MemoryBuffer> Object) {
   std::error_code EC;
   std::unique_ptr<COFFObjectFile> Ret(
       new COFFObjectFile(std::move(Object), EC));
   if (EC)
     return EC;
-  return Ret.release();
+  return std::move(Ret);
 }