Add a CallbackRegistry class to base/ to manage callbacks

base/callback_internal.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file contains utility functions and classes that help the
 // implementation, and management of the Callback objects.
 
 #ifndef BASE_CALLBACK_INTERNAL_H_
 #define BASE_CALLBACK_INTERNAL_H_
 
 #include <stddef.h>
 
 #include "base/base_export.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 
 template <typename T>
 class ScopedVector;
 
 namespace base {
 namespace internal {
 
+class CallbackListImpl;
+
 // BindStateBase is used to provide an opaque handle that the Callback
 // class can use to represent a function object with bound arguments.  It
 // behaves as an existential type that is used by a corresponding
 // DoInvoke function to perform the function execution.  This allows
 // us to shield the Callback class from the types of the bound argument via
 // "type erasure."
 class BindStateBase : public RefCountedThreadSafe<BindStateBase> {
  protected:
   friend class RefCountedThreadSafe<BindStateBase>;
   virtual ~BindStateBase() {}
@@ skipping 25 matching lines @@
   // derived Callback templates makes for much nicer compiler errors.
   explicit CallbackBase(BindStateBase* bind_state);
 
   // Force the destructor to be instantiated inside this translation unit so
   // that our subclasses will not get inlined versions.  Avoids more template
   // bloat.
   ~CallbackBase();
 
   scoped_refptr<BindStateBase> bind_state_;
   InvokeFuncStorage polymorphic_invoke_;
+
+ private:
+  friend class CallbackListImpl;
 };
 
 // This is a typetraits object that's used to take an argument type, and
 // extract a suitable type for storing and forwarding arguments.
 //
 // In particular, it strips off references, and converts arrays to
 // pointers for storage; and it avoids accidentally trying to create a
 // "reference of a reference" if the argument is a reference type.
 //
 // This array type becomes an issue for storage because we are passing bound
@@ skipping 97 matching lines @@
   return p.Pass();
 }
 
 template <typename T>
 ScopedVector<T> CallbackForward(ScopedVector<T>& p) { return p.Pass(); }
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_INTERNAL_H_