Remove IPC::ParamTraits for ui::Event.

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 e96656af4d9649fed4e6e0fd5cbb9598e0dd9485..7729f9919648390f6733cd714de6875c4fd7c4fc 100644
--- a/ui/events/keycodes/dom/dom_key.h
+++ b/ui/events/keycodes/dom/dom_key.h
@@ -10,10 +10,6 @@
 #include "base/logging.h"
 #include "build/build_config.h"
 
-#if !defined(OS_IOS)
-#include "ipc/ipc_param_traits.h"  // nogncheck
-#endif
-
 namespace ui {
 
 // Integer representation of UI Events KeyboardEvent.key value.
@@ -152,10 +148,6 @@ class DomKey {
   };
 
  private:
-#if !defined(OS_IOS)
-  friend struct IPC::ParamTraits<ui::DomKey>;
-#endif
-
   Base value_;
 };