Add flow annotation to getEventKey.

Author: mwilc0x

packages/react-dom/src/events/getEventKey.js

@@ -3,6 +3,8 @@
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
+ * 
+ * @flow
  */
 
 import getEventCharCode from './getEventCharCode';
@@ -32,49 +34,49 @@ var normalizeKey = {
  * @see https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent#Key_names
  */
 var translateToKey = {
-  8: 'Backspace',
-  9: 'Tab',
-  12: 'Clear',
-  13: 'Enter',
-  16: 'Shift',
-  17: 'Control',
-  18: 'Alt',
-  19: 'Pause',
-  20: 'CapsLock',
-  27: 'Escape',
-  32: ' ',
-  33: 'PageUp',
-  34: 'PageDown',
-  35: 'End',
-  36: 'Home',
-  37: 'ArrowLeft',
-  38: 'ArrowUp',
-  39: 'ArrowRight',
-  40: 'ArrowDown',
-  45: 'Insert',
-  46: 'Delete',
-  112: 'F1',
-  113: 'F2',
-  114: 'F3',
-  115: 'F4',
-  116: 'F5',
-  117: 'F6',
-  118: 'F7',
-  119: 'F8',
-  120: 'F9',
-  121: 'F10',
-  122: 'F11',
-  123: 'F12',
-  144: 'NumLock',
-  145: 'ScrollLock',
-  224: 'Meta',
+  '8': 'Backspace',
+  '9': 'Tab',
+  '12': 'Clear',
+  '13': 'Enter',
+  '16': 'Shift',
+  '17': 'Control',
+  '18': 'Alt',
+  '19': 'Pause',
+  '20': 'CapsLock',
+  '27': 'Escape',
+  '32': ' ',
+  '33': 'PageUp',
+  '34': 'PageDown',
+  '35': 'End',
+  '36': 'Home',
+  '37': 'ArrowLeft',
+  '38': 'ArrowUp',
+  '39': 'ArrowRight',
+  '40': 'ArrowDown',
+  '45': 'Insert',
+  '46': 'Delete',
+  '112': 'F1',
+  '113': 'F2',
+  '114': 'F3',
+  '115': 'F4',
+  '116': 'F5',
+  '117': 'F6',
+  '118': 'F7',
+  '119': 'F8',
+  '120': 'F9',
+  '121': 'F10',
+  '122': 'F11',
+  '123': 'F12',
+  '144': 'NumLock',
+  '145': 'ScrollLock',
+  '224': 'Meta',
 };
 
 /**
  * @param {object} nativeEvent Native browser event.
  * @return {string} Normalized `key` property.
  */
-function getEventKey(nativeEvent) {
+function getEventKey(nativeEvent: KeyboardEvent): string {
   if (nativeEvent.key) {
     // Normalize inconsistent values reported by browsers due to
     // implementations of a working draft specification.