Add shortcuts to audio player.

ui/file_manager/audio_player/js/audio_player.js

 // Copyright (c) 2012 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.
 
 /**
  * Overrided metadata worker's path.
  * @type {string}
  */
 ContentMetadataProvider.WORKER_SCRIPT = '/js/metadata_worker.js';
 
@@ skipping 350 matching lines @@
       break;
     case 'Ctrl-Shift-U+004A': // Ctrl+Shift+J
       chrome.fileManagerPrivate.openInspector('console');
       break;
     case 'Ctrl-Shift-U+0043': // Ctrl+Shift+C
       chrome.fileManagerPrivate.openInspector('element');
       break;
     case 'Ctrl-Shift-U+0042': // Ctrl+Shift+B
       chrome.fileManagerPrivate.openInspector('background');
       break;
+
+    case 'U+0020': // Space
+    case 'U+004B': // K
+      this.player_.$.audioController.playClick();
+      break;
+    case 'Right':

[fukino, 2016/04/14 05:42:47]

Please keep the behaviors on Up/Down.

[oka, 2016/04/14 05:55:30]

Done.

+      if (event.target.id !== 'volumeSlider')
+        this.player_.$.audioController.smallSkip(true);
+      break;
+    case 'Left':
+      if (event.target.id !== 'volumeSlider')
+        this.player_.$.audioController.smallSkip(false);
+      break;
+    case 'U+004C': // L
+      this.player_.$.audioController.bigSkip(true);
+      break;
+    case 'U+004A': // J
+      this.player_.$.audioController.bigSkip(false);
+      break;
   }
 };
 
 /* Keep the below constants in sync with the CSS. */
 
 /**
  * Window header size in pixels.
  * @type {number}
  * @const
  */
@@ skipping 206 matching lines @@
   // TODO(yoshiki): Handle error in better way.
   this.title = metadata.mediaTitle || this.getDefaultTitle();
   this.artist = error || metadata.mediaArtist || this.getDefaultArtist();
   this.artworkUrl = metadata.contentThumbnailUrl || "";
 };
 
 // Starts loading the audio player.
 window.addEventListener('DOMContentLoaded', function(e) {
   AudioPlayer.load();
 });