Add tests for autosizing before, after, first letters, and first lines

This patch adds a test for before, after, and first letter, and a second
test for first-line.

BUG=253763

Review URL: https://codereview.chromium.org/135533014

git-svn-id: svn://svn.chromium.org/blink/trunk@167072 bbb929c8-8fbe-4397-9dbb-9b2b20218538