Use the exact-width integer types defined in <stdint.h> rather than

net/base/completion_callback.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.
 
 #ifndef NET_BASE_COMPLETION_CALLBACK_H__
 #define NET_BASE_COMPLETION_CALLBACK_H__
 
 #include "base/callback.h"
 #include "base/cancelable_callback.h"
 
 namespace net {
 
 // A callback specialization that takes a single int parameter. Usually this is
 // used to report a byte count or network error code.
 typedef base::Callback<void(int)> CompletionCallback;
 
-// 64bit version of callback specialization that takes a single int64 parameter.
-// Usually this is used to report a file offset, size or network error code.
-typedef base::Callback<void(int64)> Int64CompletionCallback;
+// 64bit version of callback specialization that takes a single int64_t
+// parameter. Usually this is used to report a file offset, size or network
+// error code.
+typedef base::Callback<void(int64_t)> Int64CompletionCallback;
 
 typedef base::CancelableCallback<void(int)> CancelableCompletionCallback;
 
 }  // namespace net
 
 #endif  // NET_BASE_COMPLETION_CALLBACK_H__