Replace ToLower calls to the new format

components/language_usage_metrics/language_usage_metrics.cc

 // Copyright 2014 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.
 
 #include "components/language_usage_metrics/language_usage_metrics.h"
 
 #include <algorithm>
 
 #include "base/metrics/sparse_histogram.h"
 #include "base/strings/string_tokenizer.h"
@@ skipping 24 matching lines @@
     UMA_HISTOGRAM_SPARSE_SLOWLY("LanguageUsage.ApplicationLanguage",
                                 language_code);
 }
 
 // static
 int LanguageUsageMetrics::ToLanguageCode(const std::string& locale) {
   base::StringTokenizer parts(locale, "-_");
   if (!parts.GetNext())
     return 0;
 
-  std::string language_part = parts.token();
-  base::StringToLowerASCII(&language_part);
+  std::string language_part = base::ToLowerASCII(parts.token());
 
   int language_code = 0;
   for (std::string::iterator it = language_part.begin();
        it != language_part.end(); ++it) {
     char ch = *it;
     if (ch < 'a' || 'z' < ch)
       return 0;
 
     language_code <<= 8;
     language_code += ch;
   }
 
   return language_code;
 }
 
 // static
 void LanguageUsageMetrics::ParseAcceptLanguages(
     const std::string& accept_languages,
     std::set<int>* languages) {
   languages->clear();
   base::StringTokenizer locales(accept_languages, ",");
   while (locales.GetNext()) {
     const int language_code = ToLanguageCode(locales.token());
     if (language_code != 0)
       languages->insert(language_code);
   }
 }
 
 }  // namespace language_usage_metrics