Add some layout tests about behavior on undefined and null.

According to WebIDL in Blink guideline[1], behavior on undefind and null
must be tested in layout tests.

[1] http://www.chromium.org/blink/webidl#TOC-undefined-and-null

Review URL: https://codereview.chromium.org/289283002

git-svn-id: svn://svn.chromium.org/blink/trunk@174500 bbb929c8-8fbe-4397-9dbb-9b2b20218538