Enable sending MessagePorts to a different renderer (Chromium side)

content/browser/renderer_host/render_process_host_impl.h

Index: content/browser/renderer_host/render_process_host_impl.h
diff --git a/content/browser/renderer_host/render_process_host_impl.h b/content/browser/renderer_host/render_process_host_impl.h
index 1287b2e69493d311faa01164c00eb5b5950717c8..a056191fd10d1405f61fddf9c722686eb9683700 100644
--- a/content/browser/renderer_host/render_process_host_impl.h
+++ b/content/browser/renderer_host/render_process_host_impl.h
@@ -186,6 +186,10 @@ class CONTENT_EXPORT RenderProcessHostImpl
   }
 #endif
 
+  MessagePortMessageFilter* message_port_message_filter() const {
+    return message_port_message_filter_;
+  }
+
  protected:
   // A proxy for our IPC::Channel that lives on the IO thread (see
   // browser_process.h)