[Sync] Migrate bridge implementations to change list based MergeSyncData

components/reading_list/core/reading_list_store.cc

 // Copyright 2016 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 "components/reading_list/core/reading_list_store.h"
 
 #include <set>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 177 matching lines @@
 // Creates an object used to communicate changes in the sync metadata to the
 // model type store.
 std::unique_ptr<syncer::MetadataChangeList>
 ReadingListStore::CreateMetadataChangeList() {
   return syncer::ModelTypeStore::WriteBatch::CreateMetadataChangeList();
 }
 
 // Perform the initial merge between local and sync data. This should only be
 // called when a data type is first enabled to start syncing, and there is no
 // sync metadata. Best effort should be made to match local and sync data. The
-// keys in the |entity_data_map| will have been created via GetClientTag(...),
-// and if a local and sync data should match/merge but disagree on tags, the
-// service should use the sync data's tag. Any local pieces of data that are
-// not present in sync should immediately be Put(...) to the processor before
-// returning. The same MetadataChangeList that was passed into this function
-// can be passed to Put(...) calls. Delete(...) can also be called but should
-// not be needed for most model types. Durable storage writes, if not able to
-// combine all change atomically, should save the metadata after the data
-// changes, so that this merge will be re-driven by sync if is not completely
-// saved during the current run.
+// storage keys in the |entity_data| are populated with GetStorageKey(...),
+// local and sync copies of the same entity should resolve to the same storage
+// key. Any local pieces of data that are not present in sync should immediately
+// be Put(...) to the processor before returning. The same MetadataChangeList
+// that was passed into this function can be passed to Put(...) calls.
+// Delete(...) can also be called but should not be needed for most model types.
+// Durable storage writes, if not able to combine all change atomically, should
+// save the metadata after the data changes, so that this merge will be re-
+// driven by sync if is not completely saved during the current run.
 base::Optional<syncer::ModelError> ReadingListStore::MergeSyncData(
     std::unique_ptr<syncer::MetadataChangeList> metadata_change_list,
-    syncer::EntityDataMap entity_data_map) {
+    syncer::EntityChangeList entity_data) {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   auto token = EnsureBatchCreated();
   // Keep track of the last update of each item.
   std::set<std::string> synced_entries;
   std::unique_ptr<ReadingListModel::ScopedReadingListBatchUpdate>
       model_batch_updates = model_->BeginBatchUpdates();
 
   // Merge sync to local data.
-  for (const auto& kv : entity_data_map) {
-    synced_entries.insert(kv.first);
+  for (const auto& change : entity_data) {
+    synced_entries.insert(change.storage_key());
     const sync_pb::ReadingListSpecifics& specifics =
-        kv.second.value().specifics.reading_list();
+        change.data().specifics.reading_list();
     // Deserialize entry.
     std::unique_ptr<ReadingListEntry> entry(
         ReadingListEntry::FromReadingListSpecifics(specifics, clock_->Now()));
 
     const ReadingListEntry* existing_entry =
         model_->GetEntryByURL(entry->URL());
 
     if (!existing_entry) {
       // This entry is new. Add it to the store and model.
       // Convert to local store format and write to store.
@@ skipping 223 matching lines @@
     if (rhs.first_read_time_us() == 0 && lhs.first_read_time_us() != 0) {
       return false;
     }
     if (rhs.first_read_time_us() > lhs.first_read_time_us() &&
         lhs.first_read_time_us() != 0) {
       return false;
     }
   }
   return true;
 }