Implement features needed for local ack handling in InvalidationStateTracker.

sync/tools/null_invalidation_state_tracker.h

Index: sync/tools/null_invalidation_state_tracker.h
diff --git a/sync/tools/null_invalidation_state_tracker.h b/sync/tools/null_invalidation_state_tracker.h
new file mode 100644
index 0000000000000000000000000000000000000000..13e55c7ad1cf5d97281e9ff389765309474855e3
--- /dev/null
+++ b/sync/tools/null_invalidation_state_tracker.h
@@ -0,0 +1,40 @@
+// Copyright (c) 2012 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_TOOLS_NULL_INVALIDATION_STATE_TRACKER_H_
+#define SYNC_TOOLS_NULL_INVALIDATION_STATE_TRACKER_H_
+
+#include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
+#include "sync/notifier/invalidation_state_tracker.h"
+
+namespace syncer {
+
+class NullInvalidationStateTracker
+    : public base::SupportsWeakPtr<NullInvalidationStateTracker>,
+      public InvalidationStateTracker {
+ public:
+  NullInvalidationStateTracker();
+  virtual ~NullInvalidationStateTracker();
+
+  virtual InvalidationStateMap GetAllInvalidationStates() const OVERRIDE;
+  virtual void SetMaxVersionAndPayload(const invalidation::ObjectId& id,
+                                       int64 max_invalidation_version,
+                                       const std::string& payload) OVERRIDE;
+  virtual void Forget(const ObjectIdSet& ids) OVERRIDE;
+
+  virtual std::string GetBootstrapData() const OVERRIDE;
+  virtual void SetBootstrapData(const std::string& data) OVERRIDE;
+
+  virtual void GenerateAckHandles(
+      const ObjectIdSet& ids,
+      const scoped_refptr<base::TaskRunner>& task_runner,
+      base::Callback<void(const AckHandleMap&)> callback) OVERRIDE;
+  virtual void Acknowledge(const invalidation::ObjectId& id,
+                           const AckHandle& ack_handle) OVERRIDE;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_TOOLS_NULL_INVALIDATION_STATE_TRACKER_H_