AudioPlayer: Update control panel with playback progress bar.

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..31a48010cc1b9f4225f624ecc0a911aeb58f6b45 100644
--- a/ui/file_manager/audio_player/elements/audio_player.js
+++ b/ui/file_manager/audio_player/elements/audio_player.js
@@ -94,6 +94,12 @@ Polymer({
   },
 
   /**
+   * 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 +141,9 @@ 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));
@@ -396,6 +405,24 @@ Polymer({
   },
 
   /**
+   * Invoked then dragging state of seek bar on control panel is changed.

[yawano, 2015/10/30 01:59:53]

typo: then -> when

[fukino, 2015/10/30 04:25:53]

Done.

+   * 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.
    */