Record language usage as UMA histograms.

chrome/browser/language_usage_metrics.h

+// Copyright (c) 2011 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 CHROME_BROWSER_LANGUAGE_USAGE_METRICS_H_
+#define CHROME_BROWSER_LANGUAGE_USAGE_METRICS_H_
+#pragma once
+
+#include <set>
+#include <string>
+
+#include "base/gtest_prod_util.h"
+#include "third_party/cld/languages/public/languages.h"
+
+// Methods to record language usage as UMA histograms.
+// Language codes are defined in third_party/cld/languages/proto/languages.pb.h
+class LanguageUsageMetrics {
+ public:
+  // Records accept languages as a UMA histogram. |accept_languages| is a
+  // case-insensitive comma-separated list of languages/locales of either xx,
+  // xx-YY, or xx_YY format where xx is iso-639 language code and YY is iso-3166
+  // country code. Country code is ignored. That is, xx and XX-YY are considered
+  // identical and recorded once.
+  static void RecordAcceptLanguages(const std::string& accept_languages);
+
+  // Records the application language as a UMA histogram. |application_locale|
+  // is a case-insensitive locale string of either xx, xx-YY, or xx_YY format.
+  // Only the language part (xx in the example) is considered.
+  static void RecordApplicationLanguage(const std::string& application_locale);
+
+ private:
+  // This class must not be instantiated.
+  LanguageUsageMetrics();
+
+  // Parses |accept_languages| and returns a set of language codes in
+  // |languages|.
+  static void ParseAcceptLanguages(const std::string& accept_languages,
+                                   std::set<Language>* languages);
+
+  // Parses |locale| and returns the language code. Returns UNKNOWN_LANGUAGE in
+  // case of errors.
+  static Language ToLanguage(const std::string& locale);
+
+  FRIEND_TEST_ALL_PREFIXES(LanguageUsageMetricsTest, ParseAcceptLanguages);
+  FRIEND_TEST_ALL_PREFIXES(LanguageUsageMetricsTest, ToLanguage);
+};
+
+#endif  // CHROME_BROWSER_LANGUAGE_USAGE_METRICS_H_