components: Cleanup class/struct fwd declarations

components/sync/engine_impl/commit.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_ENGINE_IMPL_COMMIT_H_
 #define COMPONENTS_SYNC_ENGINE_IMPL_COMMIT_H_
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "components/sync/base/extensions_activity.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/base/syncer_error.h"
 #include "components/sync/engine/model_safe_worker.h"
 #include "components/sync/engine_impl/commit_contribution.h"
 #include "components/sync/engine_impl/cycle/nudge_tracker.h"
 #include "components/sync/protocol/sync.pb.h"
 
 namespace syncer {
 
 class CommitProcessor;
 class StatusController;
 class SyncCycle;
-class Syncer;
 
 // This class wraps the actions related to building and executing a single
 // commit operation.
 //
 // This class' most important responsibility is to manage the ContributionsMap.
 // This class serves as a container for those objects.  Although it would have
 // been acceptable to let this class be a dumb container object, it turns out
 // that there was no other convenient place to put the Init() and
 // PostAndProcessCommitResponse() functions.  So they ended up here.
 class Commit {
@@ skipping 36 matching lines @@
 
   // Debug only flag used to indicate if it's safe to destruct the object.
   bool cleaned_up_;
 
   DISALLOW_COPY_AND_ASSIGN(Commit);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_ENGINE_IMPL_COMMIT_H_