chrome/browser/prefs/pref_model_associator.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/prefs/pref_model_associator.h"
   6
   7 #include "base/auto_reset.h"
   8 #include "base/json/json_reader.h"
   9 #include "base/json/json_string_value_serializer.h"
  10 #include "base/location.h"
  11 #include "base/logging.h"
  12 #include "base/prefs/pref_service.h"
  13 #include "base/stl_util.h"
  14 #include "base/strings/utf_string_conversions.h"
  15 #include "base/values.h"
  16 #include "chrome/browser/prefs/pref_service_syncable.h"
  17 #include "chrome/common/pref_names.h"
  18 #include "components/content_settings/core/browser/website_settings_info.h"
  19 #include "components/content_settings/core/browser/website_settings_registry.h"
  20 #include "sync/api/sync_change.h"
  21 #include "sync/api/sync_error_factory.h"
  22 #include "sync/protocol/preference_specifics.pb.h"
  23 #include "sync/protocol/sync.pb.h"
  24
  25 using syncer::PREFERENCES;
  26 using syncer::PRIORITY_PREFERENCES;
  27
  28 namespace {
  29
  30 const sync_pb::PreferenceSpecifics& GetSpecifics(const syncer::SyncData& pref) {
  31   DCHECK(pref.GetDataType() == syncer::PREFERENCES ||
  32          pref.GetDataType() == syncer::PRIORITY_PREFERENCES);
  33   if (pref.GetDataType() == syncer::PRIORITY_PREFERENCES) {
  34     return pref.GetSpecifics().priority_preference().preference();
  35   } else {
  36     return pref.GetSpecifics().preference();
  37   }
  38 }
  39
  40 sync_pb::PreferenceSpecifics* GetMutableSpecifics(
  41     const syncer::ModelType type,
  42     sync_pb::EntitySpecifics* specifics) {
  43   if (type == syncer::PRIORITY_PREFERENCES) {
  44     DCHECK(!specifics->has_preference());
  45     return specifics->mutable_priority_preference()->mutable_preference();
  46   } else {
  47     DCHECK(!specifics->has_priority_preference());
  48     return specifics->mutable_preference();
  49   }
  50 }
  51
  52 // List of migrated preference name pairs. If a preference is migrated
  53 // (meaning renamed) adding the old and new preference names here will ensure
  54 // that the sync engine knows how to deal with the synced values coming in
  55 // with the old name. Preference migration itself doesn't happen here. It may
  56 // happen in session_startup_pref.cc.
  57 const struct MigratedPreferences {
  58   const char* const old_name;
  59   const char* const new_name;
  60 } kMigratedPreferences[] = {
  61   { prefs::kURLsToRestoreOnStartupOld, prefs::kURLsToRestoreOnStartup },
  62 };
  63
  64 std::string GetOldMigratedPreferenceName(const char* preference_name) {
  65   for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
  66     if (!strcmp(kMigratedPreferences[i].new_name, preference_name))
  67       return kMigratedPreferences[i].old_name;
  68   }
  69   return std::string();
  70 }
  71
  72 std::string GetNewMigratedPreferenceName(const char* old_preference_name) {
  73   for (size_t i = 0; i < arraysize(kMigratedPreferences); ++i) {
  74     if (!strcmp(kMigratedPreferences[i].old_name, old_preference_name))
  75       return kMigratedPreferences[i].new_name;
  76   }
  77   return std::string();
  78 }
  79
  80 }  // namespace
  81
  82 PrefModelAssociator::PrefModelAssociator(syncer::ModelType type)
  83     : models_associated_(false),
  84       processing_syncer_changes_(false),
  85       pref_service_(NULL),
  86       type_(type) {
  87   DCHECK(CalledOnValidThread());
  88   DCHECK(type_ == PREFERENCES || type_ == PRIORITY_PREFERENCES);
  89 }
  90
  91 PrefModelAssociator::~PrefModelAssociator() {
  92   DCHECK(CalledOnValidThread());
  93   pref_service_ = NULL;
  94
  95   STLDeleteContainerPairSecondPointers(synced_pref_observers_.begin(),
  96                                        synced_pref_observers_.end());
  97   synced_pref_observers_.clear();
  98 }
  99
 100 void PrefModelAssociator::InitPrefAndAssociate(
 101     const syncer::SyncData& sync_pref,
 102     const std::string& pref_name,
 103     syncer::SyncChangeList* sync_changes,
 104     SyncDataMap* migrated_preference_list) {
 105   const base::Value* user_pref_value = pref_service_->GetUserPrefValue(
 106       pref_name.c_str());
 107   VLOG(1) << "Associating preference " << pref_name;
 108
 109   if (sync_pref.IsValid()) {
 110     const sync_pb::PreferenceSpecifics& preference = GetSpecifics(sync_pref);
 111     DCHECK(pref_name == preference.name() ||
 112            (IsMigratedPreference(pref_name.c_str()) &&
 113             preference.name() ==
 114                 GetOldMigratedPreferenceName(pref_name.c_str())));
 115     base::JSONReader reader;
 116     scoped_ptr<base::Value> sync_value(reader.ReadToValue(preference.value()));
 117     if (!sync_value.get()) {
 118       LOG(ERROR) << "Failed to deserialize preference value: "
 119                  << reader.GetErrorMessage();
 120       return;
 121     }
 122
 123     if (user_pref_value) {
 124       DVLOG(1) << "Found user pref value for " << pref_name;
 125       // We have both server and local values. Merge them.
 126       scoped_ptr<base::Value> new_value(
 127           MergePreference(pref_name, *user_pref_value, *sync_value));
 128
 129       // Update the local preference based on what we got from the
 130       // sync server. Note: this only updates the user value store, which is
 131       // ignored if the preference is policy controlled.
 132       if (new_value->IsType(base::Value::TYPE_NULL)) {
 133         LOG(WARNING) << "Sync has null value for pref " << pref_name.c_str();
 134         pref_service_->ClearPref(pref_name.c_str());
 135       } else if (!new_value->IsType(user_pref_value->GetType())) {
 136         LOG(WARNING) << "Synced value for " << preference.name()
 137                      << " is of type " << new_value->GetType()
 138                      << " which doesn't match pref type "
 139                      << user_pref_value->GetType();
 140       } else if (!user_pref_value->Equals(new_value.get())) {
 141         pref_service_->Set(pref_name.c_str(), *new_value);
 142       }
 143
 144       // If the merge resulted in an updated value, inform the syncer.
 145       if (!sync_value->Equals(new_value.get())) {
 146         syncer::SyncData sync_data;
 147         if (!CreatePrefSyncData(pref_name, *new_value, &sync_data)) {
 148           LOG(ERROR) << "Failed to update preference.";
 149           return;
 150         }
 151
 152         if (IsMigratedPreference(pref_name.c_str())) {
 153           // This preference has been migrated from an old version that must be
 154           // kept in sync on older versions of Chrome.
 155           std::string old_pref_name =
 156               GetOldMigratedPreferenceName(pref_name.c_str());
 157
 158           if (preference.name() == old_pref_name) {
 159             DCHECK(migrated_preference_list);
 160             // If the name the syncer has is the old pre-migration value, then
 161             // it's possible the new migrated preference name hasn't been synced
 162             // yet. In that case the SyncChange should be an ACTION_ADD rather
 163             // than an ACTION_UPDATE. Defer the decision of whether to sync with
 164             // ACTION_ADD or ACTION_UPDATE until the migrated_preferences phase.
 165             if (migrated_preference_list)
 166               (*migrated_preference_list)[pref_name] = sync_data;
 167           } else {
 168             DCHECK_EQ(preference.name(), pref_name);
 169             sync_changes->push_back(
 170                 syncer::SyncChange(FROM_HERE,
 171                                    syncer::SyncChange::ACTION_UPDATE,
 172                                    sync_data));
 173           }
 174
 175           syncer::SyncData old_sync_data;
 176           if (!CreatePrefSyncData(old_pref_name, *new_value, &old_sync_data)) {
 177             LOG(ERROR) << "Failed to update preference.";
 178             return;
 179           }
 180           if (migrated_preference_list)
 181             (*migrated_preference_list)[old_pref_name] = old_sync_data;
 182         } else {
 183           sync_changes->push_back(
 184             syncer::SyncChange(FROM_HERE,
 185                                syncer::SyncChange::ACTION_UPDATE,
 186                                sync_data));
 187         }
 188       }
 189     } else if (!sync_value->IsType(base::Value::TYPE_NULL)) {
 190       // Only a server value exists. Just set the local user value.
 191       pref_service_->Set(pref_name.c_str(), *sync_value);
 192     } else {
 193       LOG(WARNING) << "Sync has null value for pref " << pref_name.c_str();
 194     }
 195     synced_preferences_.insert(preference.name());
 196   } else if (user_pref_value) {
 197     // The server does not know about this preference and should be added
 198     // to the syncer's database.
 199     syncer::SyncData sync_data;
 200     if (!CreatePrefSyncData(pref_name, *user_pref_value, &sync_data)) {
 201       LOG(ERROR) << "Failed to update preference.";
 202       return;
 203     }
 204     sync_changes->push_back(
 205         syncer::SyncChange(FROM_HERE,
 206                            syncer::SyncChange::ACTION_ADD,
 207                            sync_data));
 208     synced_preferences_.insert(pref_name);
 209   }
 210
 211   // Else this pref does not have a sync value but also does not have a user
 212   // controlled value (either it's a default value or it's policy controlled,
 213   // either way it's not interesting). We can ignore it. Once it gets changed,
 214   // we'll send the new user controlled value to the syncer.
 215 }
 216
 217 syncer::SyncMergeResult PrefModelAssociator::MergeDataAndStartSyncing(
 218     syncer::ModelType type,
 219     const syncer::SyncDataList& initial_sync_data,
 220     scoped_ptr<syncer::SyncChangeProcessor> sync_processor,
 221     scoped_ptr<syncer::SyncErrorFactory> sync_error_factory) {
 222   DCHECK_EQ(type_, type);
 223   DCHECK(CalledOnValidThread());
 224   DCHECK(pref_service_);
 225   DCHECK(!sync_processor_.get());
 226   DCHECK(sync_processor.get());
 227   DCHECK(sync_error_factory.get());
 228   syncer::SyncMergeResult merge_result(type);
 229   sync_processor_ = sync_processor.Pass();
 230   sync_error_factory_ = sync_error_factory.Pass();
 231
 232   syncer::SyncChangeList new_changes;
 233   std::set<std::string> remaining_preferences = registered_preferences_;
 234
 235   // Maintains a list of old migrated preference names that we wish to sync.
 236   // Keep track of these in a list such that when the preference iteration
 237   // loops below are complete we can go back and determine whether
 238   SyncDataMap migrated_preference_list;
 239
 240   // Go through and check for all preferences we care about that sync already
 241   // knows about.
 242   for (syncer::SyncDataList::const_iterator sync_iter =
 243            initial_sync_data.begin();
 244        sync_iter != initial_sync_data.end();
 245        ++sync_iter) {
 246     DCHECK_EQ(type_, sync_iter->GetDataType());
 247
 248     const sync_pb::PreferenceSpecifics& preference = GetSpecifics(*sync_iter);
 249     std::string sync_pref_name = preference.name();
 250
 251     if (remaining_preferences.count(sync_pref_name) == 0) {
 252       if (IsOldMigratedPreference(sync_pref_name.c_str())) {
 253         // This old pref name is not syncable locally anymore but we accept
 254         // changes from other Chrome installs of previous versions and migrate
 255         // them to the new name. Note that we will be merging any differences
 256         // between the new and old values and sync'ing them back.
 257         sync_pref_name = GetNewMigratedPreferenceName(sync_pref_name.c_str());
 258       } else {
 259         // We're not syncing this preference locally, ignore the sync data.
 260         // TODO(zea): Eventually we want to be able to have the syncable service
 261         // reconstruct all sync data for its datatype (therefore having
 262         // GetAllSyncData be a complete representation). We should store this
 263         // data somewhere, even if we don't use it.
 264         continue;
 265       }
 266     } else {
 267       remaining_preferences.erase(sync_pref_name);
 268     }
 269     InitPrefAndAssociate(*sync_iter, sync_pref_name, &new_changes,
 270                          &migrated_preference_list);
 271   }
 272
 273   // Go through and build sync data for any remaining preferences.
 274   for (std::set<std::string>::iterator pref_name_iter =
 275           remaining_preferences.begin();
 276        pref_name_iter != remaining_preferences.end();
 277        ++pref_name_iter) {
 278     InitPrefAndAssociate(syncer::SyncData(), *pref_name_iter, &new_changes,
 279                          &migrated_preference_list);
 280   }
 281
 282   // Now go over any migrated preference names and build sync data for them too.
 283   for (SyncDataMap::const_iterator migrated_pref_iter =
 284           migrated_preference_list.begin();
 285        migrated_pref_iter != migrated_preference_list.end();
 286        ++migrated_pref_iter) {
 287     syncer::SyncChange::SyncChangeType change_type =
 288         (synced_preferences_.count(migrated_pref_iter->first) == 0) ?
 289             syncer::SyncChange::ACTION_ADD :
 290             syncer::SyncChange::ACTION_UPDATE;
 291     new_changes.push_back(
 292         syncer::SyncChange(FROM_HERE, change_type, migrated_pref_iter->second));
 293     synced_preferences_.insert(migrated_pref_iter->first);
 294   }
 295
 296   // Push updates to sync.
 297   merge_result.set_error(
 298       sync_processor_->ProcessSyncChanges(FROM_HERE, new_changes));
 299   if (merge_result.error().IsSet())
 300     return merge_result;
 301
 302   models_associated_ = true;
 303   pref_service_->OnIsSyncingChanged();
 304   return merge_result;
 305 }
 306
 307 void PrefModelAssociator::StopSyncing(syncer::ModelType type) {
 308   DCHECK_EQ(type_, type);
 309   models_associated_ = false;
 310   sync_processor_.reset();
 311   sync_error_factory_.reset();
 312   pref_service_->OnIsSyncingChanged();
 313 }
 314
 315 scoped_ptr<base::Value> PrefModelAssociator::MergePreference(
 316     const std::string& name,
 317     const base::Value& local_value,
 318     const base::Value& server_value) {
 319   // This function special cases preferences individually, so don't attempt
 320   // to merge for all migrated values.
 321   if (name == prefs::kURLsToRestoreOnStartup ||
 322       name == prefs::kURLsToRestoreOnStartupOld) {
 323     return make_scoped_ptr(MergeListValues(local_value, server_value));
 324   }
 325
 326   content_settings::WebsiteSettingsRegistry* registry =
 327       content_settings::WebsiteSettingsRegistry::GetInstance();
 328   for (int i = 0; i < CONTENT_SETTINGS_NUM_TYPES; ++i) {
 329     ContentSettingsType type = static_cast<ContentSettingsType>(i);
 330     if (registry->Get(type)->pref_name() == name)
 331       return make_scoped_ptr(MergeDictionaryValues(local_value, server_value));
 332   }
 333
 334   // If this is not a specially handled preference, server wins.
 335   return make_scoped_ptr(server_value.DeepCopy());
 336 }
 337
 338 bool PrefModelAssociator::CreatePrefSyncData(
 339     const std::string& name,
 340     const base::Value& value,
 341     syncer::SyncData* sync_data) const {
 342   if (value.IsType(base::Value::TYPE_NULL)) {
 343     LOG(ERROR) << "Attempting to sync a null pref value for " << name;
 344     return false;
 345   }
 346
 347   std::string serialized;
 348   // TODO(zea): consider JSONWriter::Write since you don't have to check
 349   // failures to deserialize.
 350   JSONStringValueSerializer json(&serialized);
 351   if (!json.Serialize(value)) {
 352     LOG(ERROR) << "Failed to serialize preference value.";
 353     return false;
 354   }
 355
 356   sync_pb::EntitySpecifics specifics;
 357   sync_pb::PreferenceSpecifics* pref_specifics =
 358       GetMutableSpecifics(type_, &specifics);
 359
 360   pref_specifics->set_name(name);
 361   pref_specifics->set_value(serialized);
 362   *sync_data = syncer::SyncData::CreateLocalData(name, name, specifics);
 363   return true;
 364 }
 365
 366 base::Value* PrefModelAssociator::MergeListValues(const base::Value& from_value,
 367                                                   const base::Value& to_value) {
 368   if (from_value.GetType() == base::Value::TYPE_NULL)
 369     return to_value.DeepCopy();
 370   if (to_value.GetType() == base::Value::TYPE_NULL)
 371     return from_value.DeepCopy();
 372
 373   DCHECK(from_value.GetType() == base::Value::TYPE_LIST);
 374   DCHECK(to_value.GetType() == base::Value::TYPE_LIST);
 375   const base::ListValue& from_list_value =
 376       static_cast<const base::ListValue&>(from_value);
 377   const base::ListValue& to_list_value =
 378       static_cast<const base::ListValue&>(to_value);
 379   base::ListValue* result = to_list_value.DeepCopy();
 380
 381   for (base::ListValue::const_iterator i = from_list_value.begin();
 382        i != from_list_value.end(); ++i) {
 383     base::Value* value = (*i)->DeepCopy();
 384     result->AppendIfNotPresent(value);
 385   }
 386   return result;
 387 }
 388
 389 base::Value* PrefModelAssociator::MergeDictionaryValues(
 390     const base::Value& from_value,
 391     const base::Value& to_value) {
 392   if (from_value.GetType() == base::Value::TYPE_NULL)
 393     return to_value.DeepCopy();
 394   if (to_value.GetType() == base::Value::TYPE_NULL)
 395     return from_value.DeepCopy();
 396
 397   DCHECK_EQ(from_value.GetType(), base::Value::TYPE_DICTIONARY);
 398   DCHECK_EQ(to_value.GetType(), base::Value::TYPE_DICTIONARY);
 399   const base::DictionaryValue& from_dict_value =
 400       static_cast<const base::DictionaryValue&>(from_value);
 401   const base::DictionaryValue& to_dict_value =
 402       static_cast<const base::DictionaryValue&>(to_value);
 403   base::DictionaryValue* result = to_dict_value.DeepCopy();
 404
 405   for (base::DictionaryValue::Iterator it(from_dict_value); !it.IsAtEnd();
 406        it.Advance()) {
 407     const base::Value* from_key_value = &it.value();
 408     base::Value* to_key_value;
 409     if (result->GetWithoutPathExpansion(it.key(), &to_key_value)) {
 410       if (from_key_value->GetType() == base::Value::TYPE_DICTIONARY &&
 411           to_key_value->GetType() == base::Value::TYPE_DICTIONARY) {
 412         base::Value* merged_value =
 413             MergeDictionaryValues(*from_key_value, *to_key_value);
 414         result->SetWithoutPathExpansion(it.key(), merged_value);
 415       }
 416       // Note that for all other types we want to preserve the "to"
 417       // values so we do nothing here.
 418     } else {
 419       result->SetWithoutPathExpansion(it.key(), from_key_value->DeepCopy());
 420     }
 421   }
 422   return result;
 423 }
 424
 425 // static
 426 bool PrefModelAssociator::IsMigratedPreference(const char* preference_name) {
 427   return !GetOldMigratedPreferenceName(preference_name).empty();
 428 }
 429
 430 // static
 431 bool PrefModelAssociator::IsOldMigratedPreference(
 432     const char* old_preference_name) {
 433   return !GetNewMigratedPreferenceName(old_preference_name).empty();
 434 }
 435
 436 // Note: This will build a model of all preferences registered as syncable
 437 // with user controlled data. We do not track any information for preferences
 438 // not registered locally as syncable and do not inform the syncer of
 439 // non-user controlled preferences.
 440 syncer::SyncDataList PrefModelAssociator::GetAllSyncData(
 441     syncer::ModelType type)
 442     const {
 443   DCHECK_EQ(type_, type);
 444   syncer::SyncDataList current_data;
 445   for (PreferenceSet::const_iterator iter = synced_preferences_.begin();
 446        iter != synced_preferences_.end();
 447        ++iter) {
 448     std::string name = *iter;
 449     const PrefService::Preference* pref =
 450       pref_service_->FindPreference(name.c_str());
 451     DCHECK(pref);
 452     if (!pref->IsUserControlled() || pref->IsDefaultValue())
 453       continue;  // This is not data we care about.
 454     // TODO(zea): plumb a way to read the user controlled value.
 455     syncer::SyncData sync_data;
 456     if (!CreatePrefSyncData(name, *pref->GetValue(), &sync_data))
 457       continue;
 458     current_data.push_back(sync_data);
 459   }
 460   return current_data;
 461 }
 462
 463 syncer::SyncError PrefModelAssociator::ProcessSyncChanges(
 464     const tracked_objects::Location& from_here,
 465     const syncer::SyncChangeList& change_list) {
 466   if (!models_associated_) {
 467     syncer::SyncError error(FROM_HERE,
 468                             syncer::SyncError::DATATYPE_ERROR,
 469                             "Models not yet associated.",
 470                             PREFERENCES);
 471     return error;
 472   }
 473   base::AutoReset<bool> processing_changes(&processing_syncer_changes_, true);
 474   syncer::SyncChangeList::const_iterator iter;
 475   for (iter = change_list.begin(); iter != change_list.end(); ++iter) {
 476     DCHECK_EQ(type_, iter->sync_data().GetDataType());
 477
 478     const sync_pb::PreferenceSpecifics& pref_specifics =
 479         GetSpecifics(iter->sync_data());
 480
 481     std::string name = pref_specifics.name();
 482     // It is possible that we may receive a change to a preference we do not
 483     // want to sync. For example if the user is syncing a Mac client and a
 484     // Windows client, the Windows client does not support
 485     // kConfirmToQuitEnabled. Ignore updates from these preferences.
 486     const char* pref_name = name.c_str();
 487     std::string new_name;
 488     // We migrated this preference name, so do as if the name had not changed.
 489     if (IsOldMigratedPreference(pref_name)) {
 490       new_name = GetNewMigratedPreferenceName(pref_name);
 491       pref_name = new_name.c_str();
 492     }
 493
 494     if (!IsPrefRegistered(pref_name))
 495       continue;
 496
 497     if (iter->change_type() == syncer::SyncChange::ACTION_DELETE) {
 498       pref_service_->ClearPref(pref_name);
 499       continue;
 500     }
 501
 502     scoped_ptr<base::Value> value(ReadPreferenceSpecifics(pref_specifics));
 503     if (!value.get()) {
 504       // Skip values we can't deserialize.
 505       // TODO(zea): consider taking some further action such as erasing the bad
 506       // data.
 507       continue;
 508     }
 509
 510     // This will only modify the user controlled value store, which takes
 511     // priority over the default value but is ignored if the preference is
 512     // policy controlled.
 513     pref_service_->Set(pref_name, *value);
 514
 515     NotifySyncedPrefObservers(name, true /*from_sync*/);
 516
 517     // Keep track of any newly synced preferences.
 518     if (iter->change_type() == syncer::SyncChange::ACTION_ADD) {
 519       synced_preferences_.insert(name);
 520     }
 521   }
 522   return syncer::SyncError();
 523 }
 524
 525 base::Value* PrefModelAssociator::ReadPreferenceSpecifics(
 526     const sync_pb::PreferenceSpecifics& preference) {
 527   base::JSONReader reader;
 528   scoped_ptr<base::Value> value(reader.ReadToValue(preference.value()));
 529   if (!value.get()) {
 530     std::string err = "Failed to deserialize preference value: " +
 531         reader.GetErrorMessage();
 532     LOG(ERROR) << err;
 533     return NULL;
 534   }
 535   return value.release();
 536 }
 537
 538 bool PrefModelAssociator::IsPrefSynced(const std::string& name) const {
 539   return synced_preferences_.find(name) != synced_preferences_.end();
 540 }
 541
 542 void PrefModelAssociator::AddSyncedPrefObserver(const std::string& name,
 543     SyncedPrefObserver* observer) {
 544   SyncedPrefObserverList* observers = synced_pref_observers_[name];
 545   if (observers == NULL) {
 546     observers = new SyncedPrefObserverList;
 547     synced_pref_observers_[name] = observers;
 548   }
 549   observers->AddObserver(observer);
 550 }
 551
 552 void PrefModelAssociator::RemoveSyncedPrefObserver(const std::string& name,
 553     SyncedPrefObserver* observer) {
 554   SyncedPrefObserverMap::iterator observer_iter =
 555       synced_pref_observers_.find(name);
 556   if (observer_iter == synced_pref_observers_.end())
 557     return;
 558   SyncedPrefObserverList* observers = observer_iter->second;
 559   observers->RemoveObserver(observer);
 560 }
 561
 562 std::set<std::string> PrefModelAssociator::registered_preferences() const {
 563   return registered_preferences_;
 564 }
 565
 566 void PrefModelAssociator::RegisterPref(const char* name) {
 567   DCHECK(!models_associated_ && registered_preferences_.count(name) == 0);
 568   registered_preferences_.insert(name);
 569 }
 570
 571 bool PrefModelAssociator::IsPrefRegistered(const char* name) {
 572   return registered_preferences_.count(name) > 0;
 573 }
 574
 575 void PrefModelAssociator::ProcessPrefChange(const std::string& name) {
 576   if (processing_syncer_changes_)
 577     return;  // These are changes originating from us, ignore.
 578
 579   // We only process changes if we've already associated models.
 580   if (!models_associated_)
 581     return;
 582
 583   const PrefService::Preference* preference =
 584       pref_service_->FindPreference(name.c_str());
 585   if (!preference)
 586     return;
 587
 588   if (!IsPrefRegistered(name.c_str()))
 589     return;  // We are not syncing this preference.
 590
 591   syncer::SyncChangeList changes;
 592
 593   if (!preference->IsUserModifiable()) {
 594     // If the preference is no longer user modifiable, it must now be controlled
 595     // by policy, whose values we do not sync. Just return. If the preference
 596     // stops being controlled by policy, it will revert back to the user value
 597     // (which we continue to update with sync changes).
 598     return;
 599   }
 600
 601   base::AutoReset<bool> processing_changes(&processing_syncer_changes_, true);
 602
 603   NotifySyncedPrefObservers(name, false /*from_sync*/);
 604
 605   if (synced_preferences_.count(name) == 0) {
 606     // Not in synced_preferences_ means no synced data. InitPrefAndAssociate(..)
 607     // will determine if we care about its data (e.g. if it has a default value
 608     // and hasn't been changed yet we don't) and take care syncing any new data.
 609     InitPrefAndAssociate(syncer::SyncData(), name, &changes, NULL);
 610   } else {
 611     // We are already syncing this preference, just update it's sync node.
 612     syncer::SyncData sync_data;
 613     if (!CreatePrefSyncData(name, *preference->GetValue(), &sync_data)) {
 614       LOG(ERROR) << "Failed to update preference.";
 615       return;
 616     }
 617     changes.push_back(
 618         syncer::SyncChange(FROM_HERE,
 619                            syncer::SyncChange::ACTION_UPDATE,
 620                            sync_data));
 621     // This preference has been migrated from an old version that must be kept
 622     // in sync on older versions of Chrome.
 623     if (IsMigratedPreference(name.c_str())) {
 624       std::string old_pref_name = GetOldMigratedPreferenceName(name.c_str());
 625       if (!CreatePrefSyncData(old_pref_name,
 626                               *preference->GetValue(),
 627                               &sync_data)) {
 628         LOG(ERROR) << "Failed to update preference.";
 629         return;
 630       }
 631
 632       syncer::SyncChange::SyncChangeType change_type =
 633           (synced_preferences_.count(old_pref_name) == 0) ?
 634               syncer::SyncChange::ACTION_ADD :
 635               syncer::SyncChange::ACTION_UPDATE;
 636       changes.push_back(
 637           syncer::SyncChange(FROM_HERE, change_type, sync_data));
 638     }
 639   }
 640
 641   syncer::SyncError error =
 642       sync_processor_->ProcessSyncChanges(FROM_HERE, changes);
 643 }
 644
 645 void PrefModelAssociator::SetPrefService(PrefServiceSyncable* pref_service) {
 646   DCHECK(pref_service_ == NULL);
 647   pref_service_ = pref_service;
 648 }
 649
 650 void PrefModelAssociator::NotifySyncedPrefObservers(const std::string& path,
 651                                                     bool from_sync) const {
 652   SyncedPrefObserverMap::const_iterator observer_iter =
 653       synced_pref_observers_.find(path);
 654   if (observer_iter == synced_pref_observers_.end())
 655     return;
 656   SyncedPrefObserverList* observers = observer_iter->second;
 657   FOR_EACH_OBSERVER(SyncedPrefObserver, *observers,
 658                     OnSyncedPrefChanged(path, from_sync));
 659 }