Remove the use of KeyEvent.keyIdentifier.

ui/file_manager/audio_player/elements/audio_player.js

 // Copyright 2014 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.
 
 Polymer({
   is: 'audio-player',
 
   listeners: {
     'toggle-pause-event': 'onTogglePauseEvent_',
     'small-forward-skip-event': 'onSmallForwardSkipEvent_',
@@ skipping 410 matching lines @@
         this.wasPlayingOnDragStart_ = false;
       }
     }
   },
 
   /**
    * Invoked when the 'keydown' event is fired.
    * @param {Event} event The event object.
    */
   onKeyDown_: function(event) {
-    switch (event.keyIdentifier) {
-      case 'MediaNextTrack':
+    switch (event.key) {
+      case 'MediaTrackNext':
         this.onControllerNextClicked();
         break;
       case 'MediaPlayPause':
         this.playing = !this.playing;
         break;
-      case 'MediaPreviousTrack':
+      case 'MediaTrackPrevious':
         this.onControllerPreviousClicked();
         break;
       case 'MediaStop':
         // TODO: Define "Stop" behavior.
         break;
     }
   },
 
   /**
    * Computes volume value for audio element. (should be in [0.0, 1.0])
@@ skipping 37 matching lines @@
   },
 
   /**
    * Big skip backword.
    * @private
    */
   onBigBackwordSkipEvent_: function(event) {
     this.$.audioController.bigSkip(false);
   },
 });