[Sync] USS: Add EntityChange.

sync/api/entity_change.h

Index: sync/api/entity_change.h
diff --git a/sync/api/entity_change.h b/sync/api/entity_change.h
new file mode 100644
index 0000000000000000000000000000000000000000..cd572a01329e8ca369b2574a6747840081530a27
--- /dev/null
+++ b/sync/api/entity_change.h
@@ -0,0 +1,45 @@
+// Copyright 2015 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.
+
+#ifndef SYNC_API_ENTITY_CHANGE_H_
+#define SYNC_API_ENTITY_CHANGE_H_
+
+#include <string>
+
+#include "sync/api/entity_data.h"
+#include "sync/base/sync_export.h"
+
+namespace syncer_v2 {
+
+class SYNC_EXPORT EntityChange {
+ public:
+  enum ChangeType {
+    ACTION_ADD,
+    ACTION_UPDATE,
+    ACTION_DELETE
+  };
+
+  static EntityChange CreateAdd(std::string client_tag, EntityDataPtr data);
+  static EntityChange CreateUpdate(std::string client_tag, EntityDataPtr data);
+  static EntityChange CreateDelete(std::string client_tag);
+
+  virtual ~EntityChange();
+
+  std::string client_tag() const { return client_tag_; }

[skym, 2015/11/23 16:57:16]

My understanding was that we were trying to use client_key for this field going
forward.

[maxbogue, 2015/11/23 17:00:46]

Done.

+  ChangeType type() const { return type_; }
+  const EntityData& data() const { return data_.value(); }
+
+ private:
+  EntityChange(std::string client_tag, ChangeType type, EntityDataPtr data);
+
+  const std::string client_tag_;
+  const ChangeType type_;
+  const EntityDataPtr data_;
+};
+
+typedef std::vector<EntityChange> EntityChangeList;

[skym, 2015/11/23 16:57:16]

Should you have #include <vector> for this?

[maxbogue, 2015/11/23 17:00:46]

Done.

+
+}  // namespace syncer_v2
+
+#endif  // SYNC_API_ENTITY_CHANGE_H_