Don't sync kEnableContinuousSpellcheck to mobile platforms.

chrome/browser/spellchecker/spellcheck_factory.cc

 // 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.
 
 #include "chrome/browser/spellchecker/spellcheck_factory.h"
 
 #include "chrome/browser/profiles/incognito_helpers.h"
 #include "chrome/browser/spellchecker/spellcheck_service.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/grit/locale_settings.h"
@@ skipping 58 matching lines @@
 void SpellcheckServiceFactory::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* user_prefs) {
   user_prefs->RegisterListPref(prefs::kSpellCheckDictionaries,
                                new base::ListValue);
   // Continue registering kSpellCheckDictionary for preference migration.
   // TODO(estade): IDS_SPELLCHECK_DICTIONARY should be an ASCII string.
   user_prefs->RegisterStringPref(
       prefs::kSpellCheckDictionary,
       l10n_util::GetStringUTF8(IDS_SPELLCHECK_DICTIONARY));
   user_prefs->RegisterBooleanPref(prefs::kSpellCheckUseSpellingService, false);
-  user_prefs->RegisterBooleanPref(
-      prefs::kEnableContinuousSpellcheck,
-      true,
-      user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
+#if defined(OS_IOS) || defined(OS_ANDROID)
+  uint32_t flags = PrefRegistry::NO_REGISTRATION_FLAGS;
+#else
+  uint32_t flags = user_prefs::PrefRegistrySyncable::SYNCABLE_PREF;
+#endif
+  user_prefs->RegisterBooleanPref(prefs::kEnableContinuousSpellcheck, true,
+                                  flags);
 }
 
 content::BrowserContext* SpellcheckServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }
 
 bool SpellcheckServiceFactory::ServiceIsNULLWhileTesting() const {
   return true;
 }