Don't do a full document recalc when StyleResolver doesn't exist.

When removing a stylesheet, if the StyleResolver doesn't exist, we
would do a full document recalc. This is unnecessary. There's no
dependence on StyleResolver for knowing how much we need to recalc.

Also, modified the existing test a bit to make it more clear which
nodes are getting recalced.

Review URL: https://codereview.chromium.org/84993007

git-svn-id: svn://svn.chromium.org/blink/trunk@162644 bbb929c8-8fbe-4397-9dbb-9b2b20218538