rafactor(material/button): minor optimizations to button-base (#27949)

Use vararg version of classList.add which has been allowed since cac8359

also don't use a loop to check the attribute, it's only ever a single thing.

(cherry picked from commit f8c6b40)

Author: esprehn

src/material/button/button-base.ts

@@ -37,33 +37,33 @@ export const MAT_BUTTON_HOST = {
 };
 
 /** List of classes to add to buttons instances based on host attribute selector. */
-const HOST_SELECTOR_MDC_CLASS_PAIR: {selector: string; mdcClasses: string[]}[] = [
+const HOST_SELECTOR_MDC_CLASS_PAIR: {attribute: string; mdcClasses: string[]}[] = [
   {
-    selector: 'mat-button',
+    attribute: 'mat-button',
     mdcClasses: ['mdc-button', 'mat-mdc-button'],
   },
   {
-    selector: 'mat-flat-button',
+    attribute: 'mat-flat-button',
     mdcClasses: ['mdc-button', 'mdc-button--unelevated', 'mat-mdc-unelevated-button'],
   },
   {
-    selector: 'mat-raised-button',
+    attribute: 'mat-raised-button',
     mdcClasses: ['mdc-button', 'mdc-button--raised', 'mat-mdc-raised-button'],
   },
   {
-    selector: 'mat-stroked-button',
+    attribute: 'mat-stroked-button',
     mdcClasses: ['mdc-button', 'mdc-button--outlined', 'mat-mdc-outlined-button'],
   },
   {
-    selector: 'mat-fab',
+    attribute: 'mat-fab',
     mdcClasses: ['mdc-fab', 'mat-mdc-fab'],
   },
   {
-    selector: 'mat-mini-fab',
+    attribute: 'mat-mini-fab',
     mdcClasses: ['mdc-fab', 'mdc-fab--mini', 'mat-mdc-mini-fab'],
   },
   {
-    selector: 'mat-icon-button',
+    attribute: 'mat-icon-button',
     mdcClasses: ['mdc-icon-button', 'mat-mdc-icon-button'],
   },
 ];
@@ -128,15 +128,14 @@ export class MatButtonBase implements AfterViewInit, OnDestroy {
       className: 'mat-mdc-button-ripple',
     });
 
-    const classList = (_elementRef.nativeElement as HTMLElement).classList;
+    const element = this._elementRef.nativeElement;
+    const classList = (element as HTMLElement).classList;
 
     // For each of the variant selectors that is present in the button's host
     // attributes, add the correct corresponding MDC classes.
-    for (const pair of HOST_SELECTOR_MDC_CLASS_PAIR) {
-      if (this._hasHostAttributes(pair.selector)) {
-        pair.mdcClasses.forEach((className: string) => {
-          classList.add(className);
-        });
+    for (const {attribute, mdcClasses} of HOST_SELECTOR_MDC_CLASS_PAIR) {
+      if (element.hasAttribute(attribute)) {
+        classList.add(...mdcClasses);
       }
     }
   }
@@ -158,11 +157,6 @@ export class MatButtonBase implements AfterViewInit, OnDestroy {
     }
   }
 
-  /** Gets whether the button has one of the given attributes. */
-  private _hasHostAttributes(...attributes: string[]) {
-    return attributes.some(attribute => this._elementRef.nativeElement.hasAttribute(attribute));
-  }
-
   private _updateRippleDisabled(): void {
     this._rippleLoader?.setDisabled(
       this._elementRef.nativeElement,