Add code for new invalidation local ack system

sync/notifier/dropped_invalidation_tracker.cc

+// 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.
+
+#include "sync/notifier/dropped_invalidation_tracker.h"
+
+#include "sync/internal_api/public/base/invalidation.h"
+
+namespace syncer {
+
+DroppedInvalidationTracker::DroppedInvalidationTracker(
+    const invalidation::ObjectId& id)
+    : id_(id),
+      drop_ack_handle_(AckHandle::InvalidAckHandle()) {}
+
+DroppedInvalidationTracker::~DroppedInvalidationTracker() {}
+
+const invalidation::ObjectId& DroppedInvalidationTracker::object_id() const {
+  return id_;
+}
+
+void DroppedInvalidationTracker::RecordDropEvent(
+    WeakHandle<AckHandler> handler, AckHandle handle) {
+  drop_ack_handler_ = handler;
+  drop_ack_handle_ = handle;
+}
+
+void DroppedInvalidationTracker::RecordRecoveryFromDropEvent() {
+  if (drop_ack_handler_.IsInitialized()) {
+    drop_ack_handler_.Call(FROM_HERE,
+                           &AckHandler::Acknowledge,
+                           id_,
+                           drop_ack_handle_);
+  }
+  drop_ack_handler_ = syncer::WeakHandle<AckHandler>();
+}
+
+bool DroppedInvalidationTracker::IsRecoveringFromDropEvent() const {
+  return drop_ack_handler_.IsInitialized();
+}
+
+}  // namespace syncer