Implement "expand/collapse artwork" button in audio player.

ui/file_manager/audio_player/elements/track_info_panel.html

 <!--
   -- Copyright 2016 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.
   -->
 
 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
+<link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/font-roboto/roboto.html">
-<link rel="import" href="chrome-extension://hhaomjibdihmijegdhdafkllkbggdgoj/foreground/elements/files_icon_button.html">
 
 <dom-module id="track-info-panel">
   <link rel="import" type="css" href="track_info_panel.css">
   <template>
-    <div class="track">
-      <div class="icon-wrapper">
-        <div class="icon-background"></div>
-        <div class="icon" style="background-image: url([[track.artworkUrl]]);"></div>
+    <div class="track-wrapper">
+      <div class="icon-unavailable-expanded"></div>
+      <div class="icon-expanded" style="background-image: url([[track.artworkUrl]]);"></div>
+      <div class="track">
+        <div class="icon-wrapper">
+          <div class="icon" style="background-image: url([[track.artworkUrl]]);"></div>
+        </div>
+        <div class="data">
+          <div class="data-title">[[track.title]]</div>
+          <div class="data-artist">[[track.artist]]</div>
+        </div>
+        <paper-button toggles
+            id="expand"
+            class="expand"
+            active="{{expanded}}">
+        </paper-button>
       </div>
-      <div class="data">
-        <div class="data-title">[[track.title]]</div>
-        <div class="data-artist">[[track.artist]]</div>
-      </div>
-      <files-icon-button
-          id="expand"
-          class="expand"
-          on-click="expandClick">
-      </files-icon-button>
     </div>
   </template>
 </dom-module>
 
 <script src="track_info_panel.js"></script>