Change some ASSERT to CRASH to try to narrow down font crashes

This can be reverted after a few Canaries.

R=eae@chromium.org
BUG=383542

Review URL: https://codereview.chromium.org/340353004

git-svn-id: svn://svn.chromium.org/blink/trunk@176579 bbb929c8-8fbe-4397-9dbb-9b2b20218538