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

net/base/completion_callback.h

Index: net/base/completion_callback.h
diff --git a/net/base/completion_callback.h b/net/base/completion_callback.h
index 7e5c90e8bab0e872add07925218a43c531fba9dd..3b3e6055a215314547dbe9a0d6f7cb1fc851ae3b 100644
--- a/net/base/completion_callback.h
+++ b/net/base/completion_callback.h
@@ -14,9 +14,10 @@ namespace net {
 // 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;