Cleanup remaining class/struct fwd declarations

mojo/edk/system/data_pipe_consumer_dispatcher.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 MOJO_EDK_SYSTEM_DATA_PIPE_CONSUMER_DISPATCHER_H_
 #define MOJO_EDK_SYSTEM_DATA_PIPE_CONSUMER_DISPATCHER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "mojo/edk/embedder/platform_handle_vector.h"
 #include "mojo/edk/embedder/platform_shared_buffer.h"
 #include "mojo/edk/embedder/scoped_platform_handle.h"
 #include "mojo/edk/system/awakable_list.h"
 #include "mojo/edk/system/dispatcher.h"
 #include "mojo/edk/system/ports/port_ref.h"
 #include "mojo/edk/system/system_impl_export.h"
 
 namespace mojo {
 namespace edk {
 
-struct DataPipeControlMessage;
 class NodeController;
 
 // This is the Dispatcher implementation for the consumer handle for data
 // pipes created by the Mojo primitive MojoCreateDataPipe(). This class is
 // thread-safe.
 class MOJO_SYSTEM_IMPL_EXPORT DataPipeConsumerDispatcher final
     : public Dispatcher {
  public:
   DataPipeConsumerDispatcher(
       NodeController* node_controller,
@@ skipping 80 matching lines @@
   uint32_t read_offset_ = 0;
   uint32_t bytes_available_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(DataPipeConsumerDispatcher);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_DATA_PIPE_CONSUMER_DISPATCHER_H_