Reduce audio waveform layout trashing

res/css/views/voice_messages/_PlaybackContainer.scss

@@ -33,9 +33,13 @@ limitations under the License.
     font-size: $font-14px;
     line-height: $font-24px;
 
+    contain: content;
+
     .mx_Waveform {
         .mx_Waveform_bar {
             background-color: $voice-record-waveform-incomplete-fg-color;
+            height: 100%;
+            transform: scaleY(max(0.05, var(--barHeight)));
 
             &.mx_Waveform_bar_100pct {
                 // Small animation to remove the mechanical feel of progress

src/components/views/voice_messages/Waveform.tsx

@@ -34,16 +34,19 @@ interface IState {
  * For CSS purposes, a mx_Waveform_bar_100pct class is added when the bar should be
  * "filled", as a demonstration of the progress property.
  */
+
+import { CSSProperties } from "react";
+
+export interface WaveformCSSProperties extends CSSProperties {
+    '--barHeight': number;
+}
+
 @replaceableComponent("views.voice_messages.Waveform")
 export default class Waveform extends React.PureComponent<IProps, IState> {
     public static defaultProps = {
         progress: 1,
     };
 
-    public constructor(props) {
-        super(props);
-    }
-
     public render() {
         return <div className='mx_Waveform'>
             {this.props.relHeights.map((h, i) => {
@@ -53,7 +56,9 @@ export default class Waveform extends React.PureComponent<IProps, IState> {
                     'mx_Waveform_bar': true,
                     'mx_Waveform_bar_100pct': isCompleteBar,
                 });
-                return <span key={i} style={{height: (h * 100) + '%'}} className={classes} />;
+                return <span key={i} style={{
+                    "--barHeight": h,
+                } as WaveformCSSProperties} className={classes} />;
             })}
         </div>;
     }