If user profile doesn't contain language setting, default to his Google account settings.

ui/base/l10n/l10n_util.h

 // Copyright (c) 2012 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.
 
 // This file contains utility functions for dealing with localized
 // content.
 
 #ifndef UI_BASE_L10N_L10N_UTIL_H_
 #define UI_BASE_L10N_L10N_UTIL_H_
 
 #include <string>
 #include <vector>
 
 #include "base/strings/string16.h"
 #include "base/strings/string_util.h"
 #include "ui/base/ui_export.h"
 
 #if defined(OS_MACOSX)
 #include "ui/base/l10n/l10n_util_mac.h"
 #endif  // OS_MACOSX
 
 namespace l10n_util {
+// This method translates a generic locale name to one of the locally defined
+// ones. This method returns true if it succeeds.
+UI_EXPORT bool CheckAndResolveLocale(const std::string& locale,
+                                     std::string* resolved_locale);
 
 // This method is responsible for determining the locale as defined below. In
 // nearly all cases you shouldn't call this, rather use GetApplicationLocale
 // defined on browser_process.
 //
 // Returns the locale used by the Application.  First we use the value from the
 // command line (--lang), second we try the value in the prefs file (passed in
 // as |pref_locale|), finally, we fall back on the system locale. We only return
 // a value if there's a corresponding resource DLL for the locale.  Otherwise,
 // we fall back to en-us.
@@ skipping 127 matching lines @@
     const std::string& display_locale,
     std::vector<std::string>* locale_codes);
 
 // Returns the preferred size of the contents view of a window based on
 // designer given constraints which might dependent on the language used.
 UI_EXPORT int GetLocalizedContentsWidthInPixels(int pixel_resource_id);
 
 }  // namespace l10n_util
 
 #endif  // UI_BASE_L10N_L10N_UTIL_H_