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

chrome/renderer/extensions/dispatcher.cc

Index: chrome/renderer/extensions/dispatcher.cc
diff --git a/chrome/renderer/extensions/dispatcher.cc b/chrome/renderer/extensions/dispatcher.cc
index a1fd9c5d3ef5f6f757ece3a37bf72c679fb7da49..13778fed54eabf40db4538b7dfb2bb6ac07dcafe 100644
--- a/chrome/renderer/extensions/dispatcher.cc
+++ b/chrome/renderer/extensions/dispatcher.cc
@@ -595,7 +595,7 @@ void Dispatcher::OnDispatchOnConnect(
 }
 
 void Dispatcher::OnDeliverMessage(int target_port_id,
-                                  const std::string& message) {
+                                  const base::ListValue& message) {
   MiscellaneousBindings::DeliverMessage(
       v8_context_set_.GetAll(),
       target_port_id,