feat(bottom-sheet): allow focus restoration to be disabled (#13153)

Similarly to `MatDialog`, allows focus restoration to be disabled for `MatBottomSheet`.

Fixes #13150.

src/lib/bottom-sheet/bottom-sheet-config.ts

@@ -49,4 +49,10 @@ export class MatBottomSheetConfig<D = any> {
 
   /** Whether the bottom sheet should focus the first focusable element on open. */
   autoFocus?: boolean = true;
+
+  /**
+   * Whether the bottom sheet should restore focus to the
+   * previously-focused element, after it's closed.
+   */
+  restoreFocus?: boolean = true;
 }

src/lib/bottom-sheet/bottom-sheet-container.ts

@@ -190,12 +190,12 @@ export class MatBottomSheetContainer extends BasePortalOutlet implements OnDestr
     this._focusTrap.focusInitialElementWhenReady();
   }
 
-  /** Restores focus to the element that was focused before the bottom sheet opened. */
+  /** Restores focus to the element that was focused before the bottom sheet was opened. */
   private _restoreFocus() {
     const toFocus = this._elementFocusedBeforeOpened;
 
     // We need the extra check, because IE can set the `activeElement` to null in some cases.
-    if (toFocus && typeof toFocus.focus === 'function') {
+    if (this.bottomSheetConfig.restoreFocus && toFocus && typeof toFocus.focus === 'function') {
       toFocus.focus();
     }
 

src/lib/bottom-sheet/bottom-sheet.spec.ts

@@ -567,6 +567,38 @@ describe('MatBottomSheet', () => {
       document.body.removeChild(button);
     }));
 
+    it('should be able to disable focus restoration', fakeAsync(() => {
+      const button = document.createElement('button');
+      button.id = 'bottom-sheet-trigger';
+      document.body.appendChild(button);
+      button.focus();
+
+      const bottomSheetRef = bottomSheet.open(PizzaMsg, {
+        viewContainerRef: testViewContainerRef,
+        restoreFocus: false
+      });
+
+      flushMicrotasks();
+      viewContainerFixture.detectChanges();
+      flushMicrotasks();
+
+      expect(document.activeElement.id)
+          .not.toBe('bottom-sheet-trigger', 'Expected the focus to change when sheet was opened.');
+
+      bottomSheetRef.dismiss();
+      expect(document.activeElement.id).not.toBe('bottom-sheet-trigger',
+          'Expcted the focus not to have changed before the animation finishes.');
+
+      flushMicrotasks();
+      viewContainerFixture.detectChanges();
+      tick(500);
+
+      expect(document.activeElement.id).not.toBe('bottom-sheet-trigger',
+          'Expected the trigger not to be refocused on close.');
+
+      document.body.removeChild(button);
+    }));
+
   });
 
 });