Add sync manager classes for backup/rollback:

sync/internal_api/sync_backup_manager.cc

Index: sync/internal_api/sync_backup_manager.cc
diff --git a/sync/internal_api/sync_backup_manager.cc b/sync/internal_api/sync_backup_manager.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0aff436ba981b90213fea12b323eba9fb40782c1
--- /dev/null
+++ b/sync/internal_api/sync_backup_manager.cc
@@ -0,0 +1,71 @@
+// Copyright 2014 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 "sync/internal_api/sync_backup_manager.h"
+
+#include "sync/internal_api/public/write_transaction.h"
+#include "sync/syncable/directory.h"
+#include "sync/syncable/mutable_entry.h"
+
+namespace syncer {
+
+SyncBackupManager::SyncBackupManager()
+    : in_normalization_(false) {
+}
+
+SyncBackupManager::~SyncBackupManager() {
+}
+
+void SyncBackupManager::SaveChanges() {
+  NormalizeEntries();

[Nicolas Zea, 2014/04/17 18:22:56]

Is it necessary to call NormalizeEntries on every save changes? Is there any
drawback if you didn't call it at all?

[haitaol1, 2014/04/17 19:30:38]

It only checks entries that are changed, so cost is not high. Without doing
this, deleted entry is marked unsynced, which prevents them from being cleared
from memory.

+  GetUserShare()->directory->SaveChanges();
+}
+
+ModelTypeSet SyncBackupManager::HandleTransactionEndingChangeEvent(
+    const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
+    syncable::BaseTransaction* trans) {
+  ModelTypeSet types;
+  if (in_normalization_) {
+    // Skip if in our own WriteTransaction from NormalizeEntries().
+    in_normalization_ = false;
+    return types;
+  }
+
+  for (syncable::EntryKernelMutationMap::const_iterator it =
+      write_transaction_info.Get().mutations.Get().begin();
+      it != write_transaction_info.Get().mutations.Get().end(); ++it) {
+    int64 id = it->first;
+    if (unsynced_.find(id) == unsynced_.end()) {
+      unsynced_.insert(id);
+
+      const syncable::EntryKernel& e = it->second.mutated;
+      ModelType type = e.GetModelType();
+      types.Put(type);
+      if (!e.ref(syncable::ID).ServerKnows())
+        UpdateNewEntryStats(type);
+      if (e.ref(syncable::IS_DEL))
+        UpdateDeletedEntryStats(type);
+    }
+  }
+  return types;
+}
+
+void SyncBackupManager::NormalizeEntries() {
+  WriteTransaction trans(FROM_HERE, GetUserShare());
+  in_normalization_ = true;
+  for (std::set<int64>::const_iterator it = unsynced_.begin();
+      it != unsynced_.end(); ++it) {
+    syncable::MutableEntry entry(trans.GetWrappedWriteTrans(),
+                                 syncable::GET_BY_HANDLE, *it);
+    CHECK(entry.good());
+
+    if (!entry.GetId().ServerKnows())
+      entry.PutId(syncable::Id::CreateFromServerId(entry.GetId().value()));
+    entry.PutBaseVersion(1);
+    entry.PutIsUnsynced(false);
+  }
+  unsynced_.clear();
+}
+
+}  // namespace syncer