Do not use local override for language settings: always sync.

chrome/browser/profiles/profile.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.
 
 // This class gathers state related to a single user profile.
 
 #ifndef CHROME_BROWSER_PROFILES_PROFILE_H_
 #define CHROME_BROWSER_PROFILES_PROFILE_H_
 #pragma once
 
@@ skipping 467 matching lines @@
   // Returns the IO-thread-accessible profile data for this profile.
   virtual ExtensionInfoMap* GetExtensionInfoMap() = 0;
 
   // Returns the PromoCounter for Instant, or NULL if not applicable.
   virtual PromoCounter* GetInstantPromoCounter() = 0;
 
   // Gets the policy context associated with this profile.
   virtual policy::ProfilePolicyContext* GetPolicyContext() = 0;
 
 #if defined(OS_CHROMEOS)
-  // Changes application locale.
-  // "Keep local" means that changes should not be propagated to other devices.
-  virtual void ChangeApplicationLocale(
-      const std::string& locale, bool keep_local) = 0;
+  enum AppLocaleChangedVia {
+    // Caused by chrome://settings change.
+    APP_LOCALE_CHANGED_VIA_SETTINGS,
+    // Locale has been reverted via LocaleChangeGuard.
+    APP_LOCALE_CHANGED_VIA_REVERT,
+    // From login screen.
+    APP_LOCALE_CHANGED_VIA_LOGIN,
+    // Source unknown.
+    APP_LOCALE_CHANGED_VIA_UNKNOWN
+  };
+
+  // Changes application locale for a profile.
+  virtual void ChangeAppLocale(
+      const std::string& locale, AppLocaleChangedVia via) = 0;
 
   // Returns ChromeOS's ProxyConfigServiceImpl, creating if not yet created.
   virtual chromeos::ProxyConfigServiceImpl*
       GetChromeOSProxyConfigServiceImpl() = 0;
 
   // Creates ChromeOS's EnterpriseExtensionListener.
   virtual void SetupChromeOSEnterpriseExtensionObserver() = 0;
 
 #endif  // defined(OS_CHROMEOS)
 
@@ skipping 50 matching lines @@
   bool restored_last_session_;
 
   // Accessibility events will only be propagated when the pause
   // level is zero.  PauseAccessibilityEvents and ResumeAccessibilityEvents
   // increment and decrement the level, respectively, rather than set it to
   // true or false, so that calls can be nested.
   int accessibility_pause_level_;
 };
 
 #endif  // CHROME_BROWSER_PROFILES_PROFILE_H_