Refactor common invalidation framework types

sync/internal_api/public/base/ack_handle.h

Index: sync/internal_api/public/base/ack_handle.h
diff --git a/sync/internal_api/public/base/ack_handle.h b/sync/internal_api/public/base/ack_handle.h
new file mode 100644
index 0000000000000000000000000000000000000000..99d03af9eb52e7cdfaf0d5751d472d6a7c8bee37
--- /dev/null
+++ b/sync/internal_api/public/base/ack_handle.h
@@ -0,0 +1,47 @@
+// Copyright 2013 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_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H
+#define SYNC_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/time/time.h"
+#include "sync/base/sync_export.h"
+
+namespace base {
+class DictionaryValue;
+}
+
+namespace syncer {
+
+// Opaque class that represents a local ack handle. We don't reuse the
+// invalidation ack handles to avoid unnecessary dependencies.
+class SYNC_EXPORT AckHandle {
+ public:
+  static AckHandle CreateUnique();
+  static AckHandle InvalidAckHandle();
+
+  bool Equals(const AckHandle& other) const;
+
+  scoped_ptr<base::DictionaryValue> ToValue() const;
+  bool ResetFromValue(const base::DictionaryValue& value);
+
+  bool IsValid() const;
+
+  ~AckHandle();
+
+ private:
+  // Explicitly copyable and assignable for STL containers.
+  AckHandle(const std::string& state, base::Time timestamp);
+
+  std::string state_;
+  base::Time timestamp_;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_INTERNAL_API_PUBLIC_BASE_ACK_HANDLE_H