Name line-height layout tests consistently

Most of our tests have line-height in their names, but some previously had lineheight instead.

BUG=

Review URL: https://codereview.chromium.org/53483003

git-svn-id: svn://svn.chromium.org/blink/trunk@161037 bbb929c8-8fbe-4397-9dbb-9b2b20218538