Make a metaprogramming hack more C++11-compatible

Source/wtf/MemoryInstrumentation.h

Index: Source/wtf/MemoryInstrumentation.h
diff --git a/Source/wtf/MemoryInstrumentation.h b/Source/wtf/MemoryInstrumentation.h
index a16982120d7c815139179327a4b46433e7f7e712..e251d9378667e6e9013a7544c9ba40c942aab8df 100644
--- a/Source/wtf/MemoryInstrumentation.h
+++ b/Source/wtf/MemoryInstrumentation.h
@@ -134,14 +134,11 @@ private:
             void reportMemoryUsage(MemoryObjectInfo*) const { }
         };
 
-#if COMPILER(MSVC)
-#pragma warning(push)
-#pragma warning(disable: 4624) // Disable warning: destructor could not be generated because a base class destructor is inaccessible.
-#endif
-        struct Base : public Type, public BaseMixin { };
-#if COMPILER(MSVC)
-#pragma warning(pop)
-#endif
+        struct Base : public Type, public BaseMixin {
+            // Provide expicit destructor without definition to avoid MSVC warning "destructor could
+            // not be generated because a base class destructor is inaccessible."
+            ~Base();
+        };
 
         template <typename T, T t> class Helper { };