Fix for crash occuring when spatial navigation is enabled
and user tries to navigate from the element containing shadow DOM
such as <input type="date">.

BUG=234034

Review URL: https://chromiumcodereview.appspot.com/22847002

git-svn-id: svn://svn.chromium.org/blink/trunk@156839 bbb929c8-8fbe-4397-9dbb-9b2b20218538