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

content/public/browser/message_port_provider.h

Index: content/public/browser/message_port_provider.h
diff --git a/content/public/browser/message_port_provider.h b/content/public/browser/message_port_provider.h
index 1042399fdb4311c4d375458e4b65c34ebf265290..a0adec0e783bf7e2d195057b30f65017eb65f751 100644
--- a/content/public/browser/message_port_provider.h
+++ b/content/public/browser/message_port_provider.h
@@ -15,6 +15,7 @@
 namespace content {
 
 class MessagePortDelegate;
+struct MessagePortMessage;
 class WebContents;
 
 // An interface consisting of methods that can be called to use Message ports.
@@ -44,7 +45,7 @@ class CONTENT_EXPORT MessagePortProvider {
 
   // Posts a MessageEvent to a message port associated with a message channel.
   static void PostMessageToPort(int sender_port_id,
-                                const base::string16& data,
+                                const MessagePortMessage& message,
                                 const std::vector<int>& sent_ports);
 
   // Cleanup the message ports that belong to the closing delegate.