anchor.diff:      test('Entered document with a view', () {
         document.body.append(a);
         customElementsTakeRecords();
  -      expect(invocations, ['entered'],
  -          reason: 'entered callback should be invoked when entering a document '
  +      expect(invocations, ['attached'],
  +          reason: 'attached callback should be invoked when entering a document '
             'with a view');
       });
   
       test('Left document with a view', () {
         a.remove();
         customElementsTakeRecords();
  -      expect(invocations, ['left'],
  -          reason: 'left callback should be invoked when leaving a document '
  +      expect(invocations, ['detached'],
  +          reason: 'detached callback should be invoked when leaving a document '
             'with a view');
       });
   
  
positive.code:       upgradeCustomElements(s);
  
        expect(invocations, ['created'],
            reason: 'the entered callback should not be invoked when entering a '
            'Shadow DOM subtree not in the document');
      });
  
      test('Leaves Shadow DOM that is not in a document', () {
        s.innerHtml = '';
        expect(invocations, [],
            reason: 'the left callback should not be invoked when leaving a '
            'Shadow DOM subtree not in the document');
      });
  
  
negative.code:     test('Entered document without a view', () {
        docB.body.append(a);
        expect(invocations, [],
            reason: 'attached callback should not be invoked when entering a '
            'document without a view');
      });
  
  