components: Cleanup class/struct fwd declarations

components/invalidation/impl/invalidation_logger_observer.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_INVALIDATION_LOGGER_OBSERVER_H_
 #define COMPONENTS_INVALIDATION_IMPL_INVALIDATION_LOGGER_OBSERVER_H_
 
 #include "components/invalidation/public/invalidation_util.h"
 #include "components/invalidation/public/invalidator_state.h"
 #include "components/invalidation/public/object_id_invalidation_map.h"
 
 namespace base {
 class DictionaryValue;
 }  // namespace base
 
 namespace syncer {
-class InvalidationHandler;
 class ObjectIdInvalidationMap;
 }  // namespace syncer
 
 namespace invalidation {
 // This class provides the possibilty to register as an observer for the
 // InvalidationLogger notifications whenever an InvalidatorService changes
 // its internal state.
 // (i.e. A new registration, a new invalidation, a TICL/GCM state change)
 class InvalidationLoggerObserver {
  public:
   virtual void OnRegistrationChange(
       const std::multiset<std::string>& registered_handlers) = 0;
   virtual void OnStateChange(const syncer::InvalidatorState& new_state,
                              const base::Time& last_change_timestamp) = 0;
   virtual void OnUpdateIds(const std::string& handler_name,
                            const syncer::ObjectIdCountMap& details) = 0;
   virtual void OnDebugMessage(const base::DictionaryValue& details) = 0;
   virtual void OnInvalidation(
       const syncer::ObjectIdInvalidationMap& details) = 0;
   virtual void OnDetailedStatus(const base::DictionaryValue& details) = 0;
 
  protected:
   virtual ~InvalidationLoggerObserver() {}
 };
 
 }  // namespace invalidation
 
 #endif  // COMPONENTS_INVALIDATION_IMPL_INVALIDATION_LOGGER_OBSERVER_H_