Fix fast/css tests for Win7/DirectWrite by explicitly setting height

The height of text and form control can vary slightly depending on
alignment and baseline. Explicitly set height for CSS tests that do not
test nor depend on text rendering.

BUG=378610
R=dglazkov@chromium.org, eseidel@chromium.org

Review URL: https://codereview.chromium.org/323293002

git-svn-id: svn://svn.chromium.org/blink/trunk@176035 bbb929c8-8fbe-4397-9dbb-9b2b20218538