Adjust preference sync code to only sync user modifiable preferences.

chrome/browser/pref_value_store.cc

 // Copyright (c) 2010 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/pref_value_store.h"
 
 PrefValueStore::PrefValueStore(PrefStore* managed_prefs,
                                PrefStore* extension_prefs,
                                PrefStore* command_line_prefs,
                                PrefStore* user_prefs,
@@ skipping 82 matching lines @@
 
 bool PrefValueStore::PrefValueInExtensionStore(const wchar_t* name) {
   return PrefValueInStore(name, EXTENSION);
 }
 
 bool PrefValueStore::PrefValueInUserStore(const wchar_t* name) {
   return PrefValueInStore(name, USER);
 }
 
 bool PrefValueStore::PrefValueFromExtensionStore(const wchar_t* name) {
-  return PrefValueFromStore(name, EXTENSION);
+  return ControllingPrefStoreForPref(name) == EXTENSION;
 }
 
 bool PrefValueStore::PrefValueFromUserStore(const wchar_t* name) {
-  return PrefValueFromStore(name, USER);
+  return ControllingPrefStoreForPref(name) == USER;
+}
+
+bool PrefValueStore::PrefValueUserModifiable(const wchar_t* name) {
+  PrefStoreType effective_store = ControllingPrefStoreForPref(name);
+  return effective_store >= USER || effective_store == INVALID;
 }
 
 bool PrefValueStore::PrefValueInStore(const wchar_t* name, PrefStoreType type) {
   if (pref_stores_[type].get() == NULL) {
     // No store of that type set, so this pref can't be in it.
     return false;
   }
   Value* tmp_value;
   return pref_stores_[type]->prefs()->Get(name, &tmp_value);
 }
 
-bool PrefValueStore::PrefValueFromStore(const wchar_t* name,
-                                        PrefStoreType type) {
-  // No need to look in PrefStores with lower priority than the one we want.
-  for (int i = 0; i <= type; ++i) {
+PrefValueStore::PrefStoreType PrefValueStore::ControllingPrefStoreForPref(
+    const wchar_t* name) {
+  for (int i = 0; i <= PREF_STORE_TYPE_MAX; ++i) {
     if (PrefValueInStore(name, static_cast<PrefStoreType>(i)))
-      return (i == type);
+      return static_cast<PrefStoreType>(i);
   }
-  return false;
+  return INVALID;
 }