fix(material/checkbox): clear name from host node

Currently we forward the name attribute from the host node to the underlying input, however we leave the name on the host node intact. This can throw off functions like `document.getElementsByName` or the `By.name` Protractor selector.

Author: crisbeto

src/material/checkbox/checkbox.spec.ts

@@ -959,6 +959,12 @@ describe('MDC-based MatCheckbox', () => {
 
       expect(inputElement.getAttribute('name')).toBe('test-name');
     }));
+
+    it('should clear the name attribute from the host node', () => {
+      const checkboxElement = fixture.debugElement.query(By.directive(MatCheckbox));
+
+      expect(checkboxElement.nativeElement.getAttribute('name')).toBeFalsy();
+    });
   });
 
   describe('with form control', () => {

src/material/checkbox/checkbox.ts

@@ -92,6 +92,7 @@ const defaults = MAT_CHECKBOX_DEFAULT_OPTIONS_FACTORY();
     '[attr.tabindex]': 'null',
     '[attr.aria-label]': 'null',
     '[attr.aria-labelledby]': 'null',
+    '[attr.name]': 'null',
     '[class._mat-animation-noopable]': `_animationMode === 'NoopAnimations'`,
     '[class.mdc-checkbox--disabled]': 'disabled',
     '[id]': 'id',