Tidy string16.h after https://codereview.chromium.org/809563003/

base/strings/string16.h

 // Copyright 2006-2008 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 MINI_CHROMIUM_BASE_STRINGS_STRING16_H_
 #define MINI_CHROMIUM_BASE_STRINGS_STRING16_H_
 
 #include <stdint.h>
 #include <stdio.h>
 
 #include <string>
 
 #include "build/build_config.h"
 
-#if defined(WCHAR_T_IS_UTF16)
-
 namespace base {
 
+#if defined(WCHAR_T_IS_UTF16)
 typedef wchar_t char16;
-typedef std::wstring string16;
-typedef std::char_traits<wchar_t> string16_char_traits;
-
-}  // namespace base
-
 #elif defined(WCHAR_T_IS_UTF32)
-
-namespace base {
-
 typedef uint16_t char16;
-
-}  // namespace base
-
 #endif  // WCHAR_T_IS_UTF32
 
-namespace base {
-
 int c16memcmp(const char16* s1, const char16* s2, size_t n);
 size_t c16len(const char16* s);
 const char16* c16memchr(const char16* s, char16 c, size_t n);
 char16* c16memmove(char16* s1, const char16* s2, size_t n);
 char16* c16memcpy(char16* s1, const char16* s2, size_t n);
 char16* c16memset(char16* s, char16 c, size_t n);
 
-}  // namespace base
+#if defined(WCHAR_T_IS_UTF16)
 
-#if defined(WCHAR_T_IS_UTF32)
+typedef std::wstring string16;
+typedef std::char_traits<wchar_t> string16_char_traits;
 
-namespace base {
+#elif defined(WCHAR_T_IS_UTF32)
 
 struct string16_char_traits {
   typedef char16 char_type;
   typedef int int_type;
 
   static_assert(sizeof(int_type) > sizeof(char_type), "unexpected type width");
 
   typedef std::streamoff off_type;
   typedef mbstate_t state_type;
   typedef std::fpos<state_type> pos_type;
@@ skipping 52 matching lines @@
 
   static int_type eof() {
     return static_cast<int_type>(EOF);
   }
 };
 
 typedef std::basic_string<char16, base::string16_char_traits> string16;
 
 extern std::ostream& operator<<(std::ostream& out, const string16& str);
 
+#endif  // WCHAR_T_IS_UTF32
+
 }  // namespace base
 
+#if defined(WCHAR_T_IS_UTF32)
 extern template class std::basic_string<base::char16,
                                         base::string16_char_traits>;
-
 #endif  // WCHAR_T_IS_UTF32
 
 #endif  // MINI_CHROMIUM_BASE_STRINGS_STRING16_H_