Remove BindStateHolder and have Bind() return a Callback<> object directly.

net/base/completion_callback.h

 // Copyright (c) 2011 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.
 
 #ifndef NET_BASE_COMPLETION_CALLBACK_H__
 #define NET_BASE_COMPLETION_CALLBACK_H__
 #pragma once
 
 #include "base/callback_old.h"
 #include "base/callback.h"
@@ skipping 42 matching lines @@
       base::RefCounted<CancelableOldCompletionCallback<T> >::Release();
     } else {
       OldCompletionCallbackImpl<T>::RunWithParams(params);
     }
   }
 
  private:
   bool is_canceled_;
 };
 
+// Helper function for using OldCompletionCallback objects with
+// the newer CompletionCallback APIs.
+//
+// This is a transitional function and should be removed when
+// OldCompletionCallbackAdapter is deleted.
+void OldCompletionCallbackAdapter(OldCompletionCallback* old_callback, int rv);
+
 }  // namespace net
 
 #endif  // NET_BASE_COMPLETION_CALLBACK_H__