components: Cleanup class/struct fwd declarations

components/invalidation/impl/invalidator_registrar.h

 // Copyright 2014 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 COMPONENTS_INVALIDATION_IMPL_INVALIDATOR_REGISTRAR_H_
 #define COMPONENTS_INVALIDATION_IMPL_INVALIDATOR_REGISTRAR_H_
 
 #include <map>
 
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "base/threading/thread_checker.h"
 #include "components/invalidation/public/invalidation_export.h"
 #include "components/invalidation/public/invalidation_handler.h"
 #include "components/invalidation/public/invalidation_util.h"
 
-namespace invalidation {
-class ObjectId;
-}  // namespace invalidation
-
 namespace syncer {
 
 class ObjectIdInvalidationMap;
 
 // A helper class for implementations of the Invalidator interface.  It helps
 // keep track of registered handlers and which object ID registrations are
 // associated with which handlers, so implementors can just reuse the logic
 // here to dispatch invalidations and other interesting notifications.
 class INVALIDATION_EXPORT InvalidatorRegistrar {
  public:
@@ skipping 57 matching lines @@
   base::ObserverList<InvalidationHandler, true> handlers_;
   HandlerIdsMap handler_to_ids_map_;
   InvalidatorState state_;
 
   DISALLOW_COPY_AND_ASSIGN(InvalidatorRegistrar);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_INVALIDATION_IMPL_INVALIDATOR_REGISTRAR_H_