Leaking locale changes is a Very Bad Idea.

chrome/browser/net/client_hints_unittest.cc

 // Copyright 2013 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 "chrome/browser/net/client_hints.h"
 
-#include <locale.h>
-
 #include "base/logging.h"
+#include "base/test/scoped_locale.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class ClientHintsTest : public testing::Test {
  public:
   void UpdateScreenInfo(float pixel_ratio) {
     client_hints_.UpdateScreenInfo(pixel_ratio);
   };
 
  protected:
   ClientHints client_hints_;
 };
 
 TEST_F(ClientHintsTest, HintsWellFormatted) {
   UpdateScreenInfo(1.567f);
   std::string hint = client_hints_.GetDevicePixelRatioHeader();
   EXPECT_EQ("1.57", hint);
 }
 
 TEST_F(ClientHintsTest, HintsWellFormattedWithNonEnLocale) {
-  setlocale(LC_ALL, "fr_FR.UTF-8");
+  base::ScopedLocale locale("fr_FR.UTF-8");
   UpdateScreenInfo(1.567f);
   std::string hint = client_hints_.GetDevicePixelRatioHeader();
   EXPECT_EQ("1.57", hint);
 }
 
 TEST_F(ClientHintsTest, HintsHaveNonbogusValues) {
   UpdateScreenInfo(-1.567f);
   std::string hint = client_hints_.GetDevicePixelRatioHeader();
   EXPECT_EQ("", hint);
 
   UpdateScreenInfo(1.567f);
   hint = client_hints_.GetDevicePixelRatioHeader();
   EXPECT_EQ("1.57", hint);
 
   UpdateScreenInfo(0.0f);
   hint = client_hints_.GetDevicePixelRatioHeader();
   // Hints should be last known good values.
   EXPECT_EQ("1.57", hint);
 }