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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - CSS transition-property doesn't accept &quot;&lt;custom-ident&gt;&quot;"
   href="https://bugs.webkit.org/show_bug.cgi?id=157606">157606</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>CSS transition-property doesn't accept &quot;&lt;custom-ident&gt;&quot;
          </td>
        </tr>

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

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

        <tr>
          <th>Version</th>
          <td>WebKit Nightly Build
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Unspecified
          </td>
        </tr>

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

        <tr>
          <th>Severity</th>
          <td>Major
          </td>
        </tr>

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

        <tr>
          <th>Component</th>
          <td>CSS
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>50167214&#64;qq.com
          </td>
        </tr></table>
      <p>
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        <pre>Such as WebKit doesn't support:

transition-property: foo;
transition-property: --foo; /* CSS variables */
transition-property: -webkit-foo;
transition-property: -foo-bar;
transition-property: ðŸ‘»; /* Emoji */

transition: foo;
transition: --foo;
transition: -webkit-foo;
transition: -foo-bar;
transition: ðŸ‘»; /* Emoji */


The most important is that some of the automatic generation of prefix tools(Autoprefixer) once generated WebKit does not support the attributes with the prefix, will lead to the entire transition property failure.

e.g.

transition: -webkit-mask-position, mask-position;

This should be a perfectly valid value,other browsers do not have such a problem.</pre>
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