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        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Shadow element styles based on host attributes do not update"
   href="https://bugs.webkit.org/show_bug.cgi?id=169706">169706</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Shadow element styles based on host attributes do not update
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>Safari Technology Preview
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Macintosh
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>macOS 10.12
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>HTML DOM
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>jan&#64;component.kitchen
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>cdumez&#64;apple.com
          </td>
        </tr></table>
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        <pre>See <a href="http://jsbin.com/gubocem/edit?html,output">http://jsbin.com/gubocem/edit?html,output</a>

Expect: Clicking the indicated element updates its `toggle` attribute, which should in turn apply a style rule changing the background color. This works as expected in Chrome.

Actual: Clicking the element updates the attribute, but not the style. Using the inspector to manually disable the rule for `background` and re-enable it causes the rule to be applied as expected.

We've encountered various flavors of this bug before: <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - [Shadow]: &#64;host styles are not applied dynamically"
   href="show_bug.cgi?id=112869">https://bugs.webkit.org/show_bug.cgi?id=112869</a> and <a class="bz_bug_link 
          bz_status_RESOLVED  bz_closed"
   title="RESOLVED FIXED - Updating class name of a shadow host does not update the style applied by :host()"
   href="show_bug.cgi?id=158900">https://bugs.webkit.org/show_bug.cgi?id=158900</a>.</pre>
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