Find empty/boolean attributes in querySelector

[chrishow]

I have the need to match on 'empty' attribute values, specifically:

<div data-drupal-messages-fallback class="hidden"></div>

Attributes with no value also commonly appear as boolean attributes, for example:

<input type="checkbox" checked />

Currently, internalQuerySelectorAll() is not matching these attributes.

I have modified internalQuerySelectorAll to find these 'empty' attributes.