sync: Inject sync/'s dependency on invalidations

sync/notifier/dropped_invalidation_tracker.h

-// 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_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_
-#define SYNC_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_
-
-#include "google/cacheinvalidation/include/types.h"
-#include "sync/base/sync_export.h"
-#include "sync/internal_api/public/base/ack_handle.h"
-#include "sync/internal_api/public/util/weak_handle.h"
-#include "sync/notifier/ack_handler.h"
-
-namespace syncer {
-
-class Invalidation;
-
-// Helps InvalidationHandlers keep track of dropped invalidations for a given
-// ObjectId.
-//
-// The intent of this class is to hide some of the implementation details around
-// how the invalidations system manages dropping and drop recovery.  Any
-// invalidation handler that intends to buffer and occasionally drop
-// invalidations should keep one instance of it per registered ObjectId.
-//
-// When an invalidation handler wishes to drop an invalidation, it must provide
-// an instance of this class to that Invalidation's Drop() method.  In order to
-// indicate recovery from a drop, the handler can call this class'
-// RecordRecoveryFromDropEvent().
-//
-// Copy and assign are allowed for this class so we can use it in STL
-// containers.
-class SYNC_EXPORT DroppedInvalidationTracker {
- public:
-  explicit DroppedInvalidationTracker(const invalidation::ObjectId& id);
-  ~DroppedInvalidationTracker();
-
-  const invalidation::ObjectId& object_id() const;
-
-  // Called by Invalidation::Drop() to keep track of a drop event.
-  //
-  // Takes ownership of the internals belonging to a soon to be discarded
-  // dropped invalidation.  See also the comment for this class'
-  // |drop_ack_handler_| member.
-  void RecordDropEvent(WeakHandle<AckHandler> handler, AckHandle handle);
-
-  // Returns true if we're still recovering from a drop event.
-  bool IsRecoveringFromDropEvent() const;
-
-  // Called by the InvalidationHandler when it recovers from the drop event.
-  void RecordRecoveryFromDropEvent();
-
- private:
-  invalidation::ObjectId id_;
-  AckHandle drop_ack_handle_;
-
-  // This flag is set to true when we have dropped an invalidation and have not
-  // yet recovered from this drop event.  Note that this may not always coincide
-  // with drop_ack_handler_ being initialized because a null AckHandler could be
-  // passed in to RecordDropEvent().
-  bool recovering_from_drop_;
-
-  // A WeakHandle to the enitity responsible for persisting invalidation
-  // acknowledgement state on disk.  We can get away with using a WeakHandle
-  // because we don't care if our drop recovery message doesn't gets delivered
-  // in some shutdown cases.  If that happens, we'll have to process the
-  // invalidation state again on the next restart.  It would be a waste of time
-  // and resources, but otherwise not particularly harmful.
-  WeakHandle<AckHandler> drop_ack_handler_;
-};
-
-}  // namespace syncer
-
-#endif  // SYNC_NOTIFIER_DROPPED_INVALIDATION_TRACKER_H_