RefCounted types should not have public destructors, delegate cleanup

chrome/common/important_file_writer.h

Index: chrome/common/important_file_writer.h
diff --git a/chrome/common/important_file_writer.h b/chrome/common/important_file_writer.h
index 6209faf36dd854476e2d00cf64ec9fe2497cd588..25b558bae24af3d6e9f8f6b77a9dda7e403489f7 100644
--- a/chrome/common/important_file_writer.h
+++ b/chrome/common/important_file_writer.h
@@ -42,12 +42,13 @@ class ImportantFileWriter : public base::NonThreadSafe {
   // to also batch data serializations.
   class DataSerializer {
    public:
-    virtual ~DataSerializer() {}
-
     // Should put serialized string in |data| and return true on successful
     // serialization. Will be called on the same thread on which
     // ImportantFileWriter has been created.
     virtual bool SerializeData(std::string* data) = 0;
+
+   protected:
+    virtual ~DataSerializer() {}
   };
 
   // Initialize the writer.