IPC::ParamTraits for ui::Event (towards ui::Events over mojo IPC)

ui/events/keycodes/dom/dom_key.h

Index: ui/events/keycodes/dom/dom_key.h
diff --git a/ui/events/keycodes/dom/dom_key.h b/ui/events/keycodes/dom/dom_key.h
index cb4b5ee0eb0e04e8e5e6de80bf2bcc9e42636415..810f82137f620fff6de1681d1fe2b7f5a225fa75 100644
--- a/ui/events/keycodes/dom/dom_key.h
+++ b/ui/events/keycodes/dom/dom_key.h
@@ -8,6 +8,7 @@
 #include <stdint.h>
 
 #include "base/logging.h"
+#include "ipc/ipc_param_traits.h"
 
 namespace ui {
 
@@ -147,6 +148,8 @@ class DomKey {
   };
 
  private:
+  friend struct IPC::ParamTraits<ui::DomKey>;
+
   Base value_;
 };