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

chrome/renderer/extensions/dispatcher.h

Index: chrome/renderer/extensions/dispatcher.h
diff --git a/chrome/renderer/extensions/dispatcher.h b/chrome/renderer/extensions/dispatcher.h
index ec002adfb71cdffe453b5d07d9b9e0f88a7802ae..44e80bf44e97ad21f503d2273b15fc36d3db76cf 100644
--- a/chrome/renderer/extensions/dispatcher.h
+++ b/chrome/renderer/extensions/dispatcher.h
@@ -151,7 +151,7 @@ class Dispatcher : public content::RenderProcessObserver {
                            const std::string& channel_name,
                            const base::DictionaryValue& source_tab,
                            const ExtensionMsg_ExternalConnectionInfo& info);
-  void OnDeliverMessage(int target_port_id, const std::string& message);
+  void OnDeliverMessage(int target_port_id, const base::ListValue& message);
   void OnDispatchOnDisconnect(int port_id, const std::string& error_message);
   void OnSetFunctionNames(const std::vector<std::string>& names);
   void OnLoaded(