Audio Player: Add support for Media Keys

BUG=393346
R=yoshiki@chromium.org
TEST=Manually tested with external USB keyboard
Signed-off-by: Eduardo Lima (Etrunko) <eduardo.lima@intel.com>

Review URL: https://codereview.chromium.org/386043004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283431 0039d316-1c4b-4281-b951-d872f2087c98

ui/file_manager/file_manager/audio_player/elements/audio_player.js

@@ -339,6 +339,19 @@ Polymer('audio-player', {
         if (this.audioController.volumeSliderShown && this.model.volume > 9)
           this.model.volume -= 10;
         break;
+      case 'MediaNextTrack':
+        this.onControllerNextClicked();
+        break;
+      case 'MediaPlayPause':
+        var playing = this.audioController.playing;
+        this.onControllerPlayingChanged(playing, !playing);
+        break;
+      case 'MediaPreviousTrack':
+        this.onControllerPreviousClicked();
+        break;
+      case 'MediaStop':
+        // TODO: Define "Stop" behavior.
+        break;
     }
   },
 });