Replace JSON (de)serialization of extension messages with direct Value pickling.

chrome/common/extensions/extension_messages.h

 // Copyright (c) 2012 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.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 401 matching lines @@
 // Dispatch the Port.onConnect event for message channels.
 IPC_MESSAGE_ROUTED4(ExtensionMsg_DispatchOnConnect,
                     int /* target_port_id */,
                     std::string /* channel_name */,
                     DictionaryValue /* source_tab */,
                     ExtensionMsg_ExternalConnectionInfo)
 
 // Deliver a message sent with ExtensionHostMsg_PostMessage.
 IPC_MESSAGE_ROUTED2(ExtensionMsg_DeliverMessage,
                     int /* target_port_id */,
-                    std::string /* message */)
+                    ListValue /* message arguments, a 0-or-1 length list */)
 
 // Dispatch the Port.onDisconnect event for message channels.
 IPC_MESSAGE_ROUTED2(ExtensionMsg_DispatchOnDisconnect,
                     int /* port_id */,
                     std::string /* error_message */)
 
 // Informs the renderer what channel (dev, beta, stable, etc) is running.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_SetChannel,
                      int /* channel */)
 
@@ skipping 89 matching lines @@
                             int /* routing_id */,
                             int /* tab_id */,
                             std::string /* extension_id */,
                             std::string /* channel_name */,
                             int /* port_id */)
 
 // Send a message to an extension process.  The handle is the value returned
 // by ViewHostMsg_OpenChannelTo*.
 IPC_MESSAGE_ROUTED2(ExtensionHostMsg_PostMessage,
                     int /* port_id */,
-                    std::string /* message */)
+                    ListValue /* message arguments, a 0-or-1 length list */)
 
 // Send a message to an extension process.  The handle is the value returned
 // by ViewHostMsg_OpenChannelTo*.
 IPC_MESSAGE_CONTROL2(ExtensionHostMsg_CloseChannel,
                      int /* port_id */,
                      std::string /* error_message */)
 
 // Used to get the extension message bundle.
 IPC_SYNC_MESSAGE_CONTROL1_1(ExtensionHostMsg_GetMessageBundle,
                             std::string /* extension id */,
@@ skipping 92 matching lines @@
 // Notifies the browser process that a tab has started or stopped matching
 // certain conditions.  This message is sent in response to several events:
 //
 // * ExtensionMsg_WatchPages was received, updating the set of conditions.
 // * A new page is loaded.  This will be sent after ViewHostMsg_FrameNavigate.
 //   Currently this only fires for the main frame.
 // * Something changed on an existing frame causing the set of matching searches
 //   to change.
 IPC_MESSAGE_ROUTED1(ExtensionHostMsg_OnWatchedPageChange,
                     std::vector<std::string> /* Matching CSS selectors */)