content: Cleanup class/struct forward declarations

content/browser/devtools/devtools_protocol_handler.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 CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DEVTOOLS_PROTOCOL_HANDLER_H_
 #define CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DEVTOOLS_PROTOCOL_HANDLER_H_
 
 #include "content/browser/devtools/protocol/devtools_protocol_dispatcher.h"
 
 namespace content {
 
 class DevToolsAgentHost;
 class DevToolsAgentHostImpl;
-class DevToolsProtocolDelegate;
 
 class DevToolsProtocolHandler {
  public:
   using Response = DevToolsProtocolClient::Response;
 
   explicit DevToolsProtocolHandler(DevToolsAgentHostImpl* agent_host);
   virtual ~DevToolsProtocolHandler();
 
   void HandleMessage(int session_id, const std::string& message);
   bool HandleOptionalMessage(int session_id,
@@ skipping 16 matching lines @@
                              std::string* method);
 
   DevToolsAgentHost* agent_host_;
   DevToolsProtocolClient client_;
   DevToolsProtocolDispatcher dispatcher_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DEVTOOLS_PROTOCOL_DEVTOOLS_PROTOCOL_HANDLER_H_