Implement features needed for local ack handling in InvalidationStateTracker.

sync/notifier/invalidation_state_tracker.cc

 // 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.
 
 #include "sync/notifier/invalidation_state_tracker.h"
 
 namespace syncer {
 
+InvalidationState::InvalidationState()
+    : version(kint64min),
+      expected(AckHandle::InvalidAckHandle()),
+      current(AckHandle::InvalidAckHandle()) {
+}
+
+InvalidationState::~InvalidationState() {
+}
+
 bool operator==(const InvalidationState& lhs, const InvalidationState& rhs) {
-  return lhs.version == rhs.version;
+  return lhs.version == rhs.version &&
+      lhs.expected.Equals(rhs.expected) &&
+      lhs.current.Equals(rhs.current);
 }
 
 }  // namespace syncer