Reland MD Audio Player.

ui/file_manager/audio_player/elements/audio_player.js

Index: ui/file_manager/audio_player/elements/audio_player.js
diff --git a/ui/file_manager/audio_player/elements/audio_player.js b/ui/file_manager/audio_player/elements/audio_player.js
index 3d5fc01410f187a30115251c438f044aed636760..6c1820f4ee9cbd9ae441741b481e3f9f4eaf2867 100644
--- a/ui/file_manager/audio_player/elements/audio_player.js
+++ b/ui/file_manager/audio_player/elements/audio_player.js
@@ -90,10 +90,20 @@ Polymer({
       type: Number,
       value: 0,
       reflectToAttribute: true
+    },
+
+    ariaLabels: {
+      type: Object
     }
   },
 
   /**
+   * The last playing state when user starts dragging the seek bar.
+   * @private {boolean}
+   */
+  wasPlayingOnDragStart_: false,
+
+  /**
    * Handles change event for shuffle mode.
    * @param {boolean} shuffle
    */
@@ -135,6 +145,9 @@ Polymer({
   ready: function() {
     this.addEventListener('keydown', this.onKeyDown_.bind(this));
 
+    this.$.audioController.addEventListener('dragging-changed',
+        this.onDraggingChanged_.bind(this));
+
     this.$.audio.volume = 0;  // Temporary initial volume.
     this.$.audio.addEventListener('ended', this.onAudioEnded.bind(this));
     this.$.audio.addEventListener('error', this.onAudioError.bind(this));
@@ -275,6 +288,13 @@ Polymer({
   },
 
   /**
+   * Invoked when receivig a request to start playing the current music.
+   */
+  onPlayCurrentTrack: function() {
+    this.$.audio.play();
+  },
+
+  /**
    * Invoked when receiving a request to replay the current music from the track
    * list element.
    */
@@ -396,6 +416,24 @@ Polymer({
   },
 
   /**
+   * Invoked when dragging state of seek bar on control panel is changed.
+   * During the user is dragging it, audio playback is paused temporalily.
+   */
+  onDraggingChanged_: function() {
+    if (this.$.audioController.dragging) {
+      if (this.playing) {
+        this.wasPlayingOnDragStart_ = true;
+        this.$.audio.pause();
+      }
+    } else {
+      if (this.wasPlayingOnDragStart_) {
+        this.$.audio.play();
+        this.wasPlayingOnDragStart_ = false;
+      }
+    }
+  },
+
+  /**
    * Invoked when the 'keydown' event is fired.
    * @param {Event} event The event object.
    */