Fix issue 20944: Extension Doc bug for packaging

common/extensions/docs/static/packaging.html

 <div id="pageData-title" class="pageData">Packaging</div>
 <div id="pageData-showTOC" class="pageData">true</div>
 
 <p>
 Extensions are packaged as signed zip files
 with the file extension "crx"
 (for example, <code>myextension.crx</code>).
 Each extension has its own unique key pair.
 The public key is used as the unique identifier for the extension.
 The private key is kept private
@@ skipping 72 matching lines @@
   <li>
     Increase the version number in <code>manifest.json</code>.
   </li>
 
   <li>
     Bring up the Extensions management page
     by going to this URL: <b>chrome://extensions</b>
   </li>
 
   <li>
+    Click the <b>Pack extension</b> button.
+    A dialog appears.
+  </li>
+
+  <li>
     In the <b>Extension root directory</b> field,
     specify the path to the extension's folder &mdash;
     for example, <code>c:\myext</code>.
   </li>
 
   <li>
     In the <b>Private key file</b> field,
     specify the location of the
     already generated <code>.pem</code> file for this extension &mdash;
     for example, <code>c:\myext.pem</code>.
@@ skipping 22 matching lines @@
 </p>
 
 <pre>
 chrome.exe --pack-extension=c:\myext --pack-extension-key=c:\myext.pem
 </pre>
 
 <p>
 To suppress the dialog,
 add <code>--no-message-box</code> to the command.
 </p>