Revise ui::DomKey to unify character and non-character codes.

ui/events/ozone/layout/layout_util.h

Index: ui/events/ozone/layout/layout_util.h
diff --git a/ui/events/ozone/layout/layout_util.h b/ui/events/ozone/layout/layout_util.h
index 84d9d1ddc8e65090f05df474b7e67cffc45b7657..5a2ba52c1e08ea69a831dd28781d2fb2df50a55b 100644
--- a/ui/events/ozone/layout/layout_util.h
+++ b/ui/events/ozone/layout/layout_util.h
@@ -8,13 +8,12 @@
 // TODO(kpschoedel): consider moving this out of Ozone.
 
 #include "base/strings/string16.h"
+#include "ui/events/keycodes/dom/dom_key.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/events/ozone/layout/events_ozone_layout_export.h"
 
 namespace ui {
 
-enum class DomKey;
-
 // Returns the ui::EventFlags value associated with a modifier key,
 // or 0 (EF_NONE) if the key is not a modifier.
 EVENTS_OZONE_LAYOUT_EXPORT int ModifierDomKeyToEventFlag(DomKey key);