Add quick reference for bind/callback usage.

base/bind_internal.h

 // This file was GENERATED by command:
 //     pump.py bind_internal.h.pump
 // DO NOT EDIT BY HAND!!!
 
 
 // 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 BASE_BIND_INTERNAL_H_
 #define BASE_BIND_INTERNAL_H_
 #pragma once
 
 #include "base/bind_helpers.h"
 #include "base/callback_internal.h"
 #include "base/memory/raw_scoped_refptr_mismatch_checker.h"
 #include "base/memory/weak_ptr.h"
 #include "base/template_util.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include "base/bind_internal_win.h"
 #endif
 
 namespace base {
 namespace internal {
 
+// See base/callback.h for user documentation.
+//
+//
 // CONCEPTS:
 //  Runnable -- A type (really a type class) that has a single Run() method
 //              and a RunType typedef that corresponds to the type of Run().
 //              A Runnable can declare that it should treated like a method
 //              call by including a typedef named IsMethod.  The value of
 //              this typedef is NOT inspected, only the existence.  When a
 //              Runnable declares itself a method, Bind() will enforce special
 //              refcounting + WeakPtr handling semantics for the first
 //              parameter which is expected to be an object.
 //  Functor -- A copyable type representing something that should be called.
@@ skipping 2743 matching lines @@
   P4 p4_;
   P5 p5_;
   P6 p6_;
   P7 p7_;
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_BIND_INTERNAL_H_