[KeyboardEvent] Add embedder APIs to translate between Dom |key| enum and strings

ui/events/keycodes/dom_us_layout_data.h

 // Copyright (c) 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_EVENTS_KEYCODES_DOM_US_LAYOUT_DATA_H_
 #define UI_EVENTS_KEYCODES_DOM_US_LAYOUT_DATA_H_
 
+#include "ui/events/keycodes/keyboard_codes.h"
+
 namespace ui {
 
 // This table maps a DomCode to a printable character, assuming US layout.
 // It is used by DomCodeToUsLayoutMeaning(), which provides a fallback
 // interpretation when there is no other way to map a physical key.
 const struct PrintableCodeEntry {
   DomCode dom_code;
   base::char16 character[2];  // normal, shift
 } kPrintableCodeMap[] = {
     {DomCode::KEY_A, {'a', 'A'}},
@@ skipping 604 matching lines @@
     //  VKEY_MODECHANGE
     //  VKEY_NONAME
     //  VKEY_PA1
     //  VKEY_PACKET
     //  VKEY_PROCESSKEY
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_KEYCODES_DOM_US_LAYOUT_DATA_H_