Objects that derive from RefCounted/RefCountedThreadSafe should not have public dtors.

base/single_thread_task_runner.h

Index: base/single_thread_task_runner.h
diff --git a/base/single_thread_task_runner.h b/base/single_thread_task_runner.h
index 93f694ee73c2ff8658ac27c47c61db7beaab074b..c87e5f7ff1438c4599b18d5c146b2de89c9476ef 100644
--- a/base/single_thread_task_runner.h
+++ b/base/single_thread_task_runner.h
@@ -26,11 +26,14 @@ namespace base {
 //     order that must be run only from the thread the
 //     SingleThreadTaskRunner was created on.
 class BASE_EXPORT SingleThreadTaskRunner : public SequencedTaskRunner {
-public:
+ public:
   // A more explicit alias to RunsTasksOnCurrentThread().
   bool BelongsToCurrentThread() const {
     return RunsTasksOnCurrentThread();
   }
+
+ protected:
+  virtual ~SingleThreadTaskRunner() {}
 };
 
 }  // namespace base