Update the two remaining tests for the fast text autosizer

This patch updates the two remaining tests from the old text autosizer
for the new fast text autosizer.

cluster-list-item.html has been modified to not show the list bullets
and a comment has been added about why.

oscillation-javascript-fontsize-change.html has been updated to not
be a shrink-wrapped div. This changes the test significantly but I
think the test coverage may still be worth it.

BUG=

Review URL: https://codereview.chromium.org/356133003

git-svn-id: svn://svn.chromium.org/blink/trunk@177047 bbb929c8-8fbe-4397-9dbb-9b2b20218538