Don't use Ahem font in two tests to avoid flakiness

Ahem font is flaky on Mac and Windows because of bug 392046 and
bug 331583, so we should avoid it if possible.

BUG=378610
NOTRY=true

Review-Url: https://codereview.chromium.org/2187433004
Cr-Commit-Position: refs/heads/master@{#408040}
4 files changed