Reland MD Audio Player.

ui/file_manager/audio_player/elements/track_list.css

 /* Copyright 2014 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. */
 
 :host {
   align-items: center;
-  background: #f5f5f5;
+  background: rgb(245, 245, 245);
   bottom: 72px;  /* Room for the controls bar. */
-  color: #3d3d3d;
+  color: rgb(51, 51, 51);
   cursor: default;
   display: flex;
   flex-direction: column;
   font-size: 10pt;
   justify-content: flex-start;
   left: 0;
   overflow-x: hidden;
   overflow-y: auto;
   position: absolute;
   right: 0;
   top: 0;
 }
 
 /* Track item. */
 .track {
   align-items: center;
   display: flex;
   flex: 0 0 auto;
   flex-direction: row;
-  height: 44px;
+  height: 48px;
   justify-content: flex-start;
-  padding-left: 20px;
   width: 100%;
 }
 
 :host(:not([expanded])) > .track:not([active]) {
   display: none;
 }
 
-/* In the expanded mode the selected track is highlighted. */
-.track[active] {
-  background-color: rgb(66, 129, 244);
+:host([expanded]) > .track:hover {
+  background-color: rgba(0, 0, 0, 0.08);
+}
+
+/* Track icon. */
+.track .icon {
+  background-position: center;
+  background-repeat: no-repeat;
+  flex: none;
+  height: 32px;
+  margin: 8px;
+  pointer-events: none;
+  width: 32px;
+}
+
+.track:hover .icon {
+  background-image: -webkit-image-set(
+      url(../assets/100/playlist_play.png) 1x,
+      url(../assets/200/playlist_play.png) 2x);
+  pointer-events: auto;
+}
+
+.track[active] .icon {
+  background-image: -webkit-image-set(
+      url(../assets/100/playlist_now_playing.png) 1x,
+      url(../assets/200/playlist_now_playing.png) 2x);
 }
 
 /* Track data. */
 
 .track .data {
   display: flex;
   flex: 1 1 auto;
   flex-direction: column;
   justify-content: center;
   margin-left: 0;
   margin-right: 4px;
 }
 
 .track .data .data-title,
 .track .data .data-artist {
-  font-size: 12px;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
 
 .track .data .data-title {
-  color: #343434;
-  font-weight: bold;
+  color: rgb(51, 51, 51);
+  font-size: 13px;
+  font-weight: 500;
 }
 
 .track .data .data-artist {
-  color: #969696;
+  color: rgb(100, 100, 100);
+  font-size: 12px;
 }
-
-.track[active] .data .data-title,
-.track[active] .data .data-artist {
-  color: #fff;
-}