Don't show the import supervised user link before signin state is known.

BUG=341774

Review URL: https://codereview.chromium.org/143873023

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249704 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 249704