fix(material/slide-toggle): clear name from host node (#15505)

Along the same lines as #15422 and #15368. Clears the static `name` attribute from the slide
toggle's host node in order to prevent both the underlying input and the host from showing
up in `document.getElementsByName` or `By.name`.

(cherry picked from commit 5db1df0)

Author: crisbeto

src/material-experimental/mdc-slide-toggle/slide-toggle.spec.ts

@@ -755,6 +755,12 @@ describe('MDC-based MatSlideToggle with forms', () => {
       expect(slideToggleEl.classList).toContain('ng-invalid');
       expect(slideToggleEl.classList).not.toContain('ng-valid');
     }));
+
+    it('should clear static name attribute from the slide toggle host node', () => {
+      const hostNode = fixture.nativeElement.querySelector('.mat-mdc-slide-toggle');
+      expect(buttonElement.getAttribute('name')).toBeTruthy();
+      expect(hostNode.hasAttribute('name')).toBe(false);
+    });
   });
 
   describe('with model and change event', () => {

src/material-experimental/mdc-slide-toggle/slide-toggle.ts

@@ -69,6 +69,7 @@ export class MatSlideToggleChange {
     // Needs to be removed since it causes some a11y issues (see #21266).
     '[attr.tabindex]': 'null',
     '[attr.aria-label]': 'null',
+    '[attr.name]': 'null',
     '[attr.aria-labelledby]': 'null',
     '[class.mat-primary]': 'color === "primary"',
     '[class.mat-accent]': 'color !== "primary" && color !== "warn"',

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

@@ -872,6 +872,12 @@ describe('MatSlideToggle with forms', () => {
       expect(slideToggleEl.classList).toContain('ng-invalid');
       expect(slideToggleEl.classList).not.toContain('ng-valid');
     }));
+
+    it('should clear static name attribute from the slide toggle host node', () => {
+      const hostNode = fixture.nativeElement.querySelector('.mat-slide-toggle');
+      expect(inputElement.getAttribute('name')).toBeTruthy();
+      expect(hostNode.hasAttribute('name')).toBe(false);
+    });
   });
 
   describe('with model and change event', () => {

src/material/slide-toggle/slide-toggle.ts

@@ -87,6 +87,7 @@ const _MatSlideToggleBase = mixinTabIndex(
     '[attr.tabindex]': 'null',
     '[attr.aria-label]': 'null',
     '[attr.aria-labelledby]': 'null',
+    '[attr.name]': 'null',
     '[class.mat-checked]': 'checked',
     '[class.mat-disabled]': 'disabled',
     '[class.mat-slide-toggle-label-before]': 'labelPosition == "before"',