AudioPlayer: Update volume controls.

ui/file_manager/audio_player/elements/control_panel.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. */
 
 /* Controls bar. */
 .controls {
   align-items: center;
   background-color: white;
   display: flex;
   flex-direction: column;
   height: 96px;
   justify-content: center;
   padding: 0;
 }
 
+:host([volume-slider-shown]) .controls {
+  height: 144px;
+}
+
 .controls .upper-controls,
 .controls .lower-controls {
   box-sizing: border-box;
   height: 48px;
   padding: 8px;
   width: 100%;
 }
 
 .audio-controls {
   align-items: center;
@@ skipping 60 matching lines @@
   flex: none;
   font-size: 12px;
   position: relative;
   padding: 8px;
 }
 
 .time-controls > .time.disabled {
   opacity: 0;
 }
 
-.time-controls > paper-slider {
+paper-slider {
   --paper-slider-knob-color: rgb(64, 138, 241);
   --paper-slider-active-color: rgb(66, 133, 244);
   flex: auto;
 }
 
 .media-button.disabled,
 paper-slider.disabled {
   pointer-events: none;
 }
 
@@ skipping 114 matching lines @@
 .time-controls > .time > .current {
   align-items: center;
   display: flex;
   flex-direction: row;
   height: 100%;
   justify-content: flex-end;
   position: absolute;
   top: -1px;
 }
 
-/* Volume controls: sound button and volume slider */
-
-#volumeContainer {
-  border: 1px solid #ddd;
-  border-radius: 2px;
-  box-shadow: 0 2px 4px #777;
-  height: 110px;
-  position: fixed;
-  width: 32px;
+.volume-controls {
+  align-items: center;
+  background-color: rgb(235, 235, 235);
+  display: flex;
+  flex-direction: row;
 }
 
-#volumeContainer.default-hidden {
-  visibility: hidden;
+.volume-controls paper-slider {
+  width: 100%;
 }