fix(material-experimental/mdc-checkbox): add missing classes for checked

and disabled on host

Author: mmalerba

src/material-experimental/mdc-checkbox/checkbox.ts

@@ -77,6 +77,8 @@ const _MatCheckboxBase = mixinColor(
   host: {
     'class': 'mat-mdc-checkbox',
     '[attr.tabindex]': 'null',
+    '[class.mat-mdc-checkbox-disabled]': 'disabled',
+    '[class.mat-mdc-checkbox-checked]': 'checked',
     '[class._mat-animation-noopable]': `_animationMode === 'NoopAnimations'`,
     '[class.mdc-checkbox--disabled]': 'disabled',
     '[id]': 'id',