anchor.diff:                if (!dragHappened)
                   tooltip.remove();
               });
  +
  +        final String revisionLink = 'https://github.com/flutter/flutter/commit/${value.revision}';
  +
  +        tooltip.setInnerHtml(
  +          '${value.value}$unit\n'
  +          'Flutter revision: <a href="$revisionLink" target="_blank">${value.revision}</a>\n'
  +          'Recorded on: ${new DateTime.fromMillisecondsSinceEpoch(value.createTimestamp)}\n'
  +          'Goal: $goal$unit\n'
  +          'Baseline: $baseline$unit',
  +          validator: const _NullValidator(),
  +        );
  +
           final double left = bar.getBoundingClientRect().left;
           if (left < window.innerWidth / 2.0) {
             tooltip.style.left = '${bar.getBoundingClientRect().right + 5}px';
  
positive.code:         // Used to distinguish between clicks and drags.
          bool dragHappened = false;
          tooltip = new DivElement()
            ..text = '${value.value}$unit\n'
              'Flutter revision: ${value.revision}\n'
              'Recorded on: ${new DateTime.fromMillisecondsSinceEpoch(value.createTimestamp)}\n'
              'Goal: $goal$unit\n'
              'Baseline: $baseline$unit'
            ..classes.add('metric-value-tooltip')
            ..style.top = '${bar.getBoundingClientRect().top}px'
            ..onMouseDown.listen((_) {
  
negative.code:     _tooltip?.remove();
    }
  }
  
  class _NullValidator implements NodeValidator {
    const _NullValidator();
  
    @override
    bool allowsElement(Element element) => true;
  
    @override
    bool allowsAttribute(Element element, String attributeName, String value) => true;
  }
  