fix(button-toggle): clear static aria attributes from host nodes

Follow-up from #16938. Clears the aria-* attributes from the host node so that they're not duplicated with the underlying input.

Author: crisbeto

src/material/button-toggle/button-toggle.spec.ts

@@ -271,6 +271,7 @@ describe('MatButtonToggle without forms', () => {
         ButtonToggleWithTabindex,
         ButtonToggleWithStaticName,
         ButtonToggleWithStaticChecked,
+        ButtonToggleWithStaticAriaAttributes,
       ],
     });
 
@@ -756,6 +757,16 @@ describe('MatButtonToggle without forms', () => {
       fixture.detectChanges();
       expect(buttonElement.getAttribute('aria-label')).toBe('Super effective');
     });
+
+    it('should clear the static aria from the host node', () => {
+      const fixture = TestBed.createComponent(ButtonToggleWithStaticAriaAttributes);
+      fixture.detectChanges();
+      const hostNode: HTMLElement = fixture.nativeElement.querySelector('mat-button-toggle');
+
+      expect(hostNode.hasAttribute('aria-label')).toBe(false);
+      expect(hostNode.hasAttribute('aria-labelledby')).toBe(false);
+    });
+
   });
 
   describe('with provided aria-labelledby ', () => {
@@ -1073,3 +1084,11 @@ class ButtonToggleWithStaticChecked {
   @ViewChild(MatButtonToggleGroup) group: MatButtonToggleGroup;
   @ViewChildren(MatButtonToggle) toggles: QueryList<MatButtonToggle>;
 }
+
+
+@Component({
+  template: `
+    <mat-button-toggle aria-label="Toggle me" aria-labelledby="something"></mat-button-toggle>
+  `
+})
+class ButtonToggleWithStaticAriaAttributes {}

src/material/button-toggle/button-toggle.ts

@@ -398,6 +398,8 @@ const _MatButtonToggleMixinBase: CanDisableRippleCtor & typeof MatButtonToggleBa
     // Always reset the tabindex to -1 so it doesn't conflict with the one on the `button`,
     // but can still receive focus from things like cdkFocusInitial.
     '[attr.tabindex]': '-1',
+    '[attr.aria-label]': 'null',
+    '[attr.aria-labelledby]': 'null',
     '[attr.id]': 'id',
     '[attr.name]': 'null',
     '(focus)': 'focus()',