AudioPlayer: Update volume controls.

ui/file_manager/audio_player/elements/control_panel.css

Index: ui/file_manager/audio_player/elements/control_panel.css
diff --git a/ui/file_manager/audio_player/elements/control_panel.css b/ui/file_manager/audio_player/elements/control_panel.css
index 532d74585ff7f961f483a826bb01dbf9feb19be3..b4f63138023200740a9ae4e6af011fb91039914c 100644
--- a/ui/file_manager/audio_player/elements/control_panel.css
+++ b/ui/file_manager/audio_player/elements/control_panel.css
@@ -13,6 +13,10 @@
   padding: 0;
 }
 
+:host([volume-slider-shown]) .controls {
+  height: 144px;
+}
+
 .controls .upper-controls,
 .controls .lower-controls {
   box-sizing: border-box;
@@ -93,7 +97,7 @@
   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;
@@ -228,17 +232,13 @@ paper-slider.disabled {
   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%;
 }