Node::renderStyle() should only call nonRendererStyle() for <option> and <optgroup>

nonRendererStyle() really only exists for <option> and <optgroup> and
but renderStyle() means we get a virtual call inside renderStyle() for
all elements that are not yet rendered or are display: none which is
silly. Instead check if the node is an option or optgroup first.

Review URL: https://codereview.chromium.org/123583003

git-svn-id: svn://svn.chromium.org/blink/trunk@164439 bbb929c8-8fbe-4397-9dbb-9b2b20218538