Improve the unwrap_does_not_incur_additional_copying unit test am: 664ffef7e0

Original change: https://android-review.googlesource.com/c/platform/system/libbase/+/2007950

Change-Id: I0afb9c067ddd681506fd23200d3581b79be6bf84

result_test.cpp

diff --git a/result_test.cpp b/result_test.cpp
index 3b2b2e3..da8ab81 100644
--- a/result_test.cpp
+++ b/result_test.cpp
@@ -424,9 +424,11 @@
   const int data;
   static int copy_constructed;
   static int move_constructed;
-  MyData(int d) : data(d) {}
+  explicit MyData(int d) : data(d) {}
   MyData(const MyData& other) : data(other.data) { copy_constructed++; }
   MyData(MyData&& other) : data(other.data) { move_constructed++; }
+  MyData& operator=(const MyData&) = delete;
+  MyData& operator=(MyData&&) = delete;
 };
 
 int MyData::copy_constructed = 0;