components: Cleanup class/struct fwd declarations

components/arc/arc_bridge_service_impl.h

 // Copyright 2015 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_ARC_ARC_BRIDGE_SERVICE_IMPL_H_
 #define COMPONENTS_ARC_ARC_BRIDGE_SERVICE_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/files/scoped_file.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/task_runner.h"
 #include "components/arc/arc_bridge_service.h"
 #include "components/arc/arc_session.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
-namespace base {
-class SequencedTaskRunner;
-class SingleThreadTaskRunner;
-}  // namespace base
-
 namespace arc {
 
 // Real IPC based ArcBridgeService that is used in production.
 class ArcBridgeServiceImpl : public ArcBridgeService,
                              public ArcSession::Observer {
  public:
   // This is the factory interface to inject ArcSession instance
   // for testing purpose.
   using ArcSessionFactory = base::Callback<std::unique_ptr<ArcSession>()>;
 
@@ skipping 52 matching lines @@
 
   // WeakPtrFactory to use callbacks.
   base::WeakPtrFactory<ArcBridgeServiceImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ArcBridgeServiceImpl);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_ARC_BRIDGE_SERVICE_IMPL_H_