--- a/browser/base/content/tabbrowser.xml
+++ b/browser/base/content/tabbrowser.xml
@@ -5489,22 +5489,16 @@
             modifiedAttrs.push("soundplaying-scheduledremoval");
           }
 
           if (!tab.hasAttribute("soundplaying")) {
             tab.setAttribute("soundplaying", true);
             modifiedAttrs.push("soundplaying");
           }
 
-          if (modifiedAttrs.length) {
-            // Flush style so that the opacity takes effect immediately, in
-            // case the media is stopped before the style flushes naturally.
-            getComputedStyle(tab).opacity;
-          }
-
           this._tabAttrModified(tab, modifiedAttrs);
         ]]>
       </handler>
       <handler event="DOMAudioPlaybackStopped">
         <![CDATA[
           var tab = this.getTabFromAudioEvent(event)
           if (!tab) {
             return;