refactor(cdk/a11y): use classList.toggle

With Angular dropping IE11 support in version 13, we can now use `classList.toggle` with the second `force` param. Related to #7374

Author: jelbourn

src/cdk/a11y/focus-monitor/focus-monitor.ts

@@ -308,14 +308,6 @@ export class FocusMonitor implements OnDestroy {
     return doc.defaultView || window;
   }
 
-  private _toggleClass(element: Element, className: string, shouldSet: boolean) {
-    if (shouldSet) {
-      element.classList.add(className);
-    } else {
-      element.classList.remove(className);
-    }
-  }
-
   private _getFocusOrigin(focusEventTarget: HTMLElement | null): FocusOrigin {
     if (this._origin) {
       // If the origin was realized via a touch interaction, we need to perform additional checks
@@ -368,11 +360,11 @@ export class FocusMonitor implements OnDestroy {
    * @param origin The focus origin.
    */
   private _setClasses(element: HTMLElement, origin?: FocusOrigin): void {
-    this._toggleClass(element, 'cdk-focused', !!origin);
-    this._toggleClass(element, 'cdk-touch-focused', origin === 'touch');
-    this._toggleClass(element, 'cdk-keyboard-focused', origin === 'keyboard');
-    this._toggleClass(element, 'cdk-mouse-focused', origin === 'mouse');
-    this._toggleClass(element, 'cdk-program-focused', origin === 'program');
+    element.classList.toggle('cdk-focused', !!origin);
+    element.classList.toggle('cdk-touch-focused', origin === 'touch');
+    element.classList.toggle('cdk-keyboard-focused', origin === 'keyboard');
+    element.classList.toggle('cdk-mouse-focused', origin === 'mouse');
+    element.classList.toggle('cdk-program-focused', origin === 'program');
   }
 
   /**