Update write checks for external extension file on mac.

chrome/common/extensions/docs/static/external_extensions.html

Index: chrome/common/extensions/docs/static/external_extensions.html
diff --git a/chrome/common/extensions/docs/static/external_extensions.html b/chrome/common/extensions/docs/static/external_extensions.html
index 6f95a914e36228025ee28fea439d5c58b0b13cea..5dcbeecc907ed19688e1c35c647bce7e31e08656 100644
--- a/chrome/common/extensions/docs/static/external_extensions.html
+++ b/chrome/common/extensions/docs/static/external_extensions.html
@@ -103,7 +103,7 @@ or <code>/home/share/extension.crx</code>.)
     </dd>
   <dt> Mac OS X: </dt>
     <dd> <code>/Library/Application Support/Google/Chrome/External Extensions/</code> </dd>
-    <p class="note"><b>Note:</b> The external extensions file is read only if every directory in the path is owned by the user <code>root</code>, has the group <code>admin</code>, and is not world readable.  The path must also be free of symbolic links.  These restrictions prevent an unprivileged user from causing extensions to be installed for all users.  See <a href="#troubleshooting">troubleshooting</a> for details.</p>
+    <p class="note"><b>Note:</b> The external extensions file is read only if every directory in the path is owned by the user <code>root</code>, has the group <code>admin</code> or <code>wheel</code>, and is not world readable.  The path must also be free of symbolic links.  These restrictions prevent an unprivileged user from causing extensions to be installed for all users.  See <a href="#troubleshooting">troubleshooting</a> for details.</p>

[Mark Mentovai, 2011/10/17 18:53:57]

As before.

[Sam Kerner (Chrome), 2011/10/17 19:35:16]

Done.

     <p class="note">
     <b>Note:</b> The above path was added in Chrome 16.  Prior versions used a different path, which is now deprecated:
     <code>/Applications/Google Chrome.app/Contents/Extensions/</code> .</p>