Add workaround for VS2005 compile error introduced by r70933

base/observer_list_threadsafe.h

Index: base/observer_list_threadsafe.h
diff --git a/base/observer_list_threadsafe.h b/base/observer_list_threadsafe.h
index 6085fde74ba9093ec59edf38e53c4f57eb65f7db..ecdad90ccebc20e4ab685b7f46aa3375587a72fc 100644
--- a/base/observer_list_threadsafe.h
+++ b/base/observer_list_threadsafe.h
@@ -49,9 +49,32 @@
 //   will notify its regular ObserverList.
 //
 ///////////////////////////////////////////////////////////////////////////////
+
+// Forward declaration for ObserverListThreadSafeTraits.
+template <class ObserverType>
+class ObserverListThreadSafe;
+
+// This class is used to work around VS2005 not accepting:
+//
+// friend class
+//     base::RefCountedThreadSafe<ObserverListThreadSafe<ObserverType> >;
+//
+// Instead of friending the class, we could friend the actual function
+// which calls delete.  However, this ends up being
+// RefCountedThreadSafe::DeleteInternal(), which is private.  So we
+// define our own templated traits class so we can friend it.
+template <class T>
+struct ObserverListThreadSafeTraits {
+  static void Destruct(const ObserverListThreadSafe<T>* x) {
+    delete x;
+  }
+};
+
 template <class ObserverType>
 class ObserverListThreadSafe
-    : public base::RefCountedThreadSafe<ObserverListThreadSafe<ObserverType> > {
+    : public base::RefCountedThreadSafe<
+        ObserverListThreadSafe<ObserverType>,
+        ObserverListThreadSafeTraits<ObserverType> > {
  public:
   typedef typename ObserverList<ObserverType>::NotificationType
       NotificationType;
@@ -130,8 +153,9 @@ class ObserverListThreadSafe
   // TODO(mbelshe):  Add more wrappers for Notify() with more arguments.
 
  private:
-  friend class
-      base::RefCountedThreadSafe<ObserverListThreadSafe<ObserverType> >;
+  // See comment above ObserverListThreadSafeTraits' definition.
+  friend struct ObserverListThreadSafeTraits<ObserverType>;
+
   ~ObserverListThreadSafe() {
     typename ObserversListMap::const_iterator it;
     for (it = observer_lists_.begin(); it != observer_lists_.end(); ++it)