RefCounted types should not have public destructors, delegate cleanup

chrome/browser/extensions/extension_pref_value_map.h

Index: chrome/browser/extensions/extension_pref_value_map.h
diff --git a/chrome/browser/extensions/extension_pref_value_map.h b/chrome/browser/extensions/extension_pref_value_map.h
index e03123b56f6742018bf9e844f166523c400dd750..2cde315f8e1148de4a482e207eaeeb15a8c0fd56 100644
--- a/chrome/browser/extensions/extension_pref_value_map.h
+++ b/chrome/browser/extensions/extension_pref_value_map.h
@@ -59,8 +59,6 @@ class ExtensionPrefValueMap : public ProfileKeyedService {
   // Observer interface for monitoring ExtensionPrefValueMap.
   class Observer {
    public:
-    virtual ~Observer() {}
-
     // Called when the value for the given |key| set by one of the extensions
     // changes. This does not necessarily mean that the effective value has
     // changed.
@@ -70,6 +68,9 @@ class ExtensionPrefValueMap : public ProfileKeyedService {
     // Called when the ExtensionPrefValueMap is being destroyed. When called,
     // observers must unsubscribe.
     virtual void OnExtensionPrefValueMapDestruction() = 0;
+
+   protected:
+    virtual ~Observer() {}
   };
 
   ExtensionPrefValueMap();