Restore Mute button for Android media element.

Source/core/css/mediaControlsAndroid.css

Index: Source/core/css/mediaControlsAndroid.css
diff --git a/Source/core/css/mediaControlsAndroid.css b/Source/core/css/mediaControlsAndroid.css
index 60deeb72ef5a6dae5e57271dcd57a1558fc197b8..70cec724dff3eebe6b149969d633b1b4cd532b49 100644
--- a/Source/core/css/mediaControlsAndroid.css
+++ b/Source/core/css/mediaControlsAndroid.css
@@ -42,10 +42,6 @@ audio::-webkit-media-controls-panel, video::-webkit-media-controls-panel {
     height: 35px;
 }
 
-audio::-webkit-media-controls-mute-button, video::-webkit-media-controls-mute-button {
-    display: none;
-}
-
 audio::-webkit-media-controls-play-button, video::-webkit-media-controls-play-button {
     width: 35px;
     height: 35px;