feat(button-toggle): Add aria-label and aria-labelledby to button toggle

src/lib/button-toggle/button-toggle.html

@@ -5,6 +5,8 @@
          [checked]="checked"
          [disabled]="disabled || null"
          [name]="name"
+         [attr.aria-label]="ariaLabel"
+         [attr.aria-labelledby]="ariaLabelledby"
          (change)="_onInputChange($event)"
          (click)="_onInputClick($event)">
 

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

@@ -218,6 +218,8 @@ describe('MdButtonToggle without forms', () => {
         ButtonTogglesInsideButtonToggleGroupMultiple,
         ButtonToggleGroupWithInitialValue,
         StandaloneButtonToggle,
+        ButtonToggleWithAriaLabel,
+        ButtonToggleWithAriaLabelledby,
       ],
     });
 
@@ -592,8 +594,49 @@ describe('MdButtonToggle without forms', () => {
     });
 
   });
-});
 
+  describe('with provided aria-label ', () => {
+    let checkboxDebugElement: DebugElement;
+    let checkboxNativeElement: HTMLElement;
+    let inputElement: HTMLInputElement;
+
+    it('should use the provided aria-label', () => {
+      let fixture = TestBed.createComponent(ButtonToggleWithAriaLabel);
+      checkboxDebugElement = fixture.debugElement.query(By.directive(MdButtonToggle));
+      checkboxNativeElement = checkboxDebugElement.nativeElement;
+      inputElement = checkboxNativeElement.querySelector('input') as HTMLInputElement;
+
+      fixture.detectChanges();
+      expect(inputElement.getAttribute('aria-label')).toBe('Super effective');
+    });
+  });
+
+  describe('with provided aria-labelledby ', () => {
+    let checkboxDebugElement: DebugElement;
+    let checkboxNativeElement: HTMLElement;
+    let inputElement: HTMLInputElement;
+
+    it('should use the provided aria-labelledby', () => {
+      let fixture = TestBed.createComponent(ButtonToggleWithAriaLabelledby);
+      checkboxDebugElement = fixture.debugElement.query(By.directive(MdButtonToggle));
+      checkboxNativeElement = checkboxDebugElement.nativeElement;
+      inputElement = checkboxNativeElement.querySelector('input') as HTMLInputElement;
+
+      fixture.detectChanges();
+      expect(inputElement.getAttribute('aria-labelledby')).toBe('some-id');
+    });
+
+    it('should not assign aria-labelledby if none is provided', () => {
+      let fixture = TestBed.createComponent(StandaloneButtonToggle);
+      checkboxDebugElement = fixture.debugElement.query(By.directive(MdButtonToggle));
+      checkboxNativeElement = checkboxDebugElement.nativeElement;
+      inputElement = checkboxNativeElement.querySelector('input') as HTMLInputElement;
+
+      fixture.detectChanges();
+      expect(inputElement.getAttribute('aria-labelledby')).toBe(null);
+    });
+  });
+});
 
 @Component({
   template: `
@@ -674,3 +717,15 @@ class ButtonToggleGroupWithInitialValue {
 class ButtonToggleGroupWithFormControl {
   control = new FormControl();
 }
+
+/** Simple test component with an aria-label set. */
+@Component({
+  template: `<md-button-toggle aria-label="Super effective"></md-button-toggle>`
+})
+class ButtonToggleWithAriaLabel { }
+
+/** Simple test component with an aria-label set. */
+@Component({
+  template: `<md-button-toggle aria-labelledby="some-id"></md-button-toggle>`
+})
+class ButtonToggleWithAriaLabelledby {}

src/lib/button-toggle/button-toggle.ts

@@ -277,6 +277,17 @@ export class MdButtonToggleGroupMultiple extends _MdButtonToggleGroupMixinBase
   }
 })
 export class MdButtonToggle implements OnInit, OnDestroy {
+  /**
+   * Attached to the aria-label attribute of the host element. In most cases, arial-labelledby will
+   * take precedence so this may be omitted.
+   */
+  @Input('aria-label') ariaLabel: string = '';
+
+  /**
+   * Users can specify the `aria-labelledby` attribute which will be forwarded to the input element
+   */
+  @Input('aria-labelledby') ariaLabelledby: string | null = null;
+
   /** Whether or not this button toggle is checked. */
   private _checked: boolean = false;