Reland MD Audio Player.

ui/file_manager/audio_player/elements/track_list.js

Index: ui/file_manager/audio_player/elements/track_list.js
diff --git a/ui/file_manager/audio_player/elements/track_list.js b/ui/file_manager/audio_player/elements/track_list.js
index 95894edfd8bc4f3fa654395f33a088949537b641..d1a030e4652d785364e0e65fbcaf147161580a52 100644
--- a/ui/file_manager/audio_player/elements/track_list.js
+++ b/ui/file_manager/audio_player/elements/track_list.js
@@ -166,8 +166,15 @@ var TrackInfo;
     trackClicked: function(event) {
       var index = ~~event.currentTarget.getAttribute('index');
       var track = this.tracks[index];
-      if (track)
-        this.selectTrack(track);
+      if (track) {
+        if (event.target.classList.contains('icon')) {
+          // If the play icon on the track is clicked, change the current track
+          // and start playing it regardless of current play state.
+          this.selectTrack(track, true /* force to play */);
+        } else {
+          this.selectTrack(track, false /* force to play */);
+        }
+      }
     },
 
     /**
@@ -250,8 +257,10 @@ var TrackInfo;
      * Sets the current track.
      * @param {!TrackInfo} track TrackInfo to be set as the current
      *     track.
+     * @param {boolean} forceToPlay True if the track should be played
+     *     regardless of the current play state (paused/played).
      */
-    selectTrack: function(track) {
+    selectTrack: function(track, forceToPlay) {
       var index = -1;
       for (var i = 0; i < this.tracks.length; i++) {
         if (this.tracks[i].url === track.url) {
@@ -261,10 +270,13 @@ var TrackInfo;
       }
       if (index >= 0) {
         // TODO(yoshiki): Clean up the flow and the code around here.
-        if (this.currentTrackIndex == index)
+        if (this.currentTrackIndex === index) {
           this.replayCurrentTrack();
-        else
+        } else {
           this.currentTrackIndex = index;
+          if (forceToPlay)
+            this.fire('play');
+        }
       }
     },