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

chrome/renderer/extensions/extension_helper.cc

Index: chrome/renderer/extensions/extension_helper.cc
diff --git a/chrome/renderer/extensions/extension_helper.cc b/chrome/renderer/extensions/extension_helper.cc
index c61221bbb8db7a7a65f07b1cfb708cbd09f901ca..a5e7ef48347afc013c0d161442927ac040bf6f32 100644
--- a/chrome/renderer/extensions/extension_helper.cc
+++ b/chrome/renderer/extensions/extension_helper.cc
@@ -274,8 +274,9 @@ void ExtensionHelper::OnExtensionDispatchOnConnect(
       render_view());
 }
 
-void ExtensionHelper::OnExtensionDeliverMessage(int target_id,
-                                                const std::string& message) {
+void ExtensionHelper::OnExtensionDeliverMessage(
+    int target_id,
+    const base::ListValue& message) {
   MiscellaneousBindings::DeliverMessage(dispatcher_->v8_context_set().GetAll(),
                                         target_id,
                                         message,