Optionally have MessagePort pass data as base::Value, part 1.

content/public/browser/message_port_delegate.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_PUBLIC_BROWSER_MESSAGE_PORT_DELEGATE_H_
 #define CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_DELEGATE_H_
 
 #include <vector>
 
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
 
 // Windows headers will redefine SendMessage.
 #ifdef SendMessage
 #undef SendMessage
 #endif
 
 namespace content {
+struct MessagePortMessage;
 
 // Delegate used by MessagePortService to send messages to message ports to the
 // correct renderer. Delegates are responsible for managing their own lifetime,
 // and should call MessagePortService::OnMessagePortDelegateClosing if they are
 // destroyed while there are still message ports associated with them.
 class CONTENT_EXPORT MessagePortDelegate {
  public:
   // Sends a message to the given route. Implementations are responsible for
   // updating MessagePortService with new routes for the sent message ports.
   virtual void SendMessage(int route_id,
-                           const base::string16& message,
+                           const MessagePortMessage& message,
                            const std::vector<int>& sent_message_port_ids) = 0;
 
   // Requests messages to the given route to be queued.
   virtual void SendMessagesAreQueued(int route_id) = 0;
 
  protected:
   virtual ~MessagePortDelegate() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_MESSAGE_PORT_DELEGATE_H_