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

content/common/message_port_messages.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.
 
 // Defines messages between the browser and worker process, as well as between
 // the renderer and worker process.
 
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
+#include "content/public/common/message_port_types.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_message_utils.h"
 
 #undef IPC_MESSAGE_EXPORT
 #define IPC_MESSAGE_EXPORT CONTENT_EXPORT
 #define IPC_MESSAGE_START MessagePortMsgStart
 
 // Singly-included section, not converted.

[Tom Sepez, 2015/02/27 18:16:05]

nit: As long as you're mucking with this, my comment at this line is getting a
little out of date.  Changing this to
// Singly-included section for typedefs.
would be appreciated by me.  Thanks.

[Marijn Kruisselbrink, 2015/02/27 18:20:15]

Done.

 #ifndef CONTENT_COMMON_MESSAGE_PORT_MESSAGES_H_
 #define CONTENT_COMMON_MESSAGE_PORT_MESSAGES_H_
 
-typedef std::pair<base::string16, std::vector<int> > QueuedMessage;
+typedef std::pair<content::MessagePortMessage, std::vector<int>> QueuedMessage;
 
 #endif  // CONTENT_COMMON_MESSAGE_PORT_MESSAGES_H_
 
+IPC_STRUCT_TRAITS_BEGIN(content::MessagePortMessage)
+  IPC_STRUCT_TRAITS_MEMBER(message_as_string)
+  IPC_STRUCT_TRAITS_MEMBER(message_as_value)
+IPC_STRUCT_TRAITS_END()
+
 //-----------------------------------------------------------------------------
 // MessagePort messages
 // These are messages sent from the browser to child processes.
 
 // Sends a message to a message port.
 IPC_MESSAGE_ROUTED3(MessagePortMsg_Message,
-                    base::string16 /* message */,
+                    content::MessagePortMessage /* message */,
                     std::vector<int> /* sent_message_port_ids */,
                     std::vector<int> /* new_routing_ids */)
 
 // Tells the Message Port Channel object that there are no more in-flight
 // messages arriving.
 IPC_MESSAGE_ROUTED0(MessagePortMsg_MessagesQueued)
 
 //-----------------------------------------------------------------------------
 // MessagePortHost messages
 // These are messages sent from child processes to the browser.
 
 // Creates a new Message Port Channel object.  The first paramaeter is the
 // message port channel's routing id in this process.  The second parameter
 // is the process-wide-unique identifier for that port.
 IPC_SYNC_MESSAGE_CONTROL0_2(MessagePortHostMsg_CreateMessagePort,
                             int /* route_id */,
                             int /* message_port_id */)
 
 // Sent when a Message Port Channel object is destroyed.
 IPC_MESSAGE_CONTROL1(MessagePortHostMsg_DestroyMessagePort,
                      int /* message_port_id */)
 
 // Sends a message to a message port.  Optionally sends a message port as
 // as well if sent_message_port_id != MSG_ROUTING_NONE.
 IPC_MESSAGE_CONTROL3(MessagePortHostMsg_PostMessage,
                      int /* sender_message_port_id */,
-                     base::string16 /* message */,
+                     content::MessagePortMessage /* message */,
                      std::vector<int> /* sent_message_port_ids */)
 
 // Causes messages sent to the remote port to be delivered to this local port.
 IPC_MESSAGE_CONTROL2(MessagePortHostMsg_Entangle,
                      int /* local_message_port_id */,
                      int /* remote_message_port_id */)
 
 // Causes the browser to queue messages sent to this port until the the port
 // has made sure that all in-flight messages were routed to the new
 // destination.
 IPC_MESSAGE_CONTROL1(MessagePortHostMsg_QueueMessages,
                      int /* message_port_id */)
 
 // Sends the browser all the queued messages that arrived at this message port
 // after it was sent in a postMessage call.
 // NOTE: MSVS can't compile the macro if std::vector<std::pair<string16, int> >
 // is used, so we typedef it in worker_messages.h.
 IPC_MESSAGE_CONTROL2(MessagePortHostMsg_SendQueuedMessages,
                      int /* message_port_id */,
                      std::vector<QueuedMessage> /* queued_messages */)
 
 // Tells the browser this message port is ready to receive messages. If the
 // browser was holding messages to this port because no destination for the
 // port was available yet this will cause the browser to release those messages.
 IPC_MESSAGE_CONTROL1(MessagePortHostMsg_ReleaseMessages,
                      int /* message_port_id */)