[Sync] Replace typedef with using.

components/sync/model/string_ordinal.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 COMPONENTS_SYNC_MODEL_STRING_ORDINAL_H_
 #define COMPONENTS_SYNC_MODEL_STRING_ORDINAL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "components/sync/base/ordinal.h"
 
 namespace syncer {
 
 // A StringOrdinal is an Ordinal with range 'a'-'z' for printability
 // of its internal byte string representation.  (Think of
 // StringOrdinal as being short for PrintableStringOrdinal.)  It
 // should be used for data types that want to maintain one or more
 // orderings for nodes.
 //
 // Since StringOrdinals contain only printable characters, it is safe
 // to store as a string in a protobuf.
 
 struct StringOrdinalTraits {
   static const uint8_t kZeroDigit = 'a';
   static const uint8_t kMaxDigit = 'z';
   static const size_t kMinLength = 1;
 };
 
-typedef Ordinal<StringOrdinalTraits> StringOrdinal;
+using StringOrdinal = Ordinal<StringOrdinalTraits>;
 
 static_assert(StringOrdinal::kZeroDigit == 'a',
               "StringOrdinal has incorrect zero digit");
 static_assert(StringOrdinal::kOneDigit == 'b',
               "StringOrdinal has incorrect one digit");
 static_assert(StringOrdinal::kMidDigit == 'n',
               "StringOrdinal has incorrect mid digit");
 static_assert(StringOrdinal::kMaxDigit == 'z',
               "StringOrdinal has incorrect max digit");
 static_assert(StringOrdinal::kMidDigitValue == 13,
               "StringOrdinal has incorrect mid digit value");
 static_assert(StringOrdinal::kMaxDigitValue == 25,
               "StringOrdinal has incorrect max digit value");
 static_assert(StringOrdinal::kRadix == 26, "StringOrdinal has incorrect radix");
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_MODEL_STRING_ORDINAL_H_