Extend with a language code in http accept languages

net/http/http_util_icu.h

+// Copyright (c) 2016 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_HTTP_HTTP_UTIL_ICU_H_
+#define NET_HTTP_HTTP_UTIL_ICU_H_
+
+#include <string>
+
+#include "net/base/net_export.h"
+
+namespace net {
+
+class NET_EXPORT HttpUtilIcu {
+ public:
+  // Given a comma separated ordered list of language codes, return

[Seigo Nonaka, 2016/12/12 01:48:54]

nit: continue line until 80 chars.

[Yirui Huang, 2016/12/12 06:50:41]

Done.

+  // the list with a qvalue appended to each language.
+  // The way qvalues are assigned is rather simple. The qvalue
+  // starts with 1.0 and is decremented by 0.2 for each successive entry
+  // in the list until it reaches 0.2. All the entries after that are
+  // assigned the same qvalue of 0.2. Also, note that the 1st language
+  // will not have a qvalue added because the absence of a qvalue implicitly
+  // means q=1.0.
+  //
+  // When making a http request, this should be used to determine what
+  // to put in Accept-Language header. If a comma separated list of language
+  // codes *without* qvalue is sent, web servers regard all
+  // of them as having q=1.0 and pick one of them even though it may not
+  // be at the beginning of the list (see http://crbug.com/5899).
+  static std::string GenerateAcceptLanguageHeader(
+      const std::string& raw_language_list);
+};
+}  // namespace net
+
+#endif  // NET_HTTP_HTTP_UTIL_ICU_H_