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

This reverts commit 6a597f4387bac05620550918ff078ab0ab085d4b.

TBR=eae@chromium.org
BUG=383542

Review URL: https://codereview.chromium.org/335993005

git-svn-id: svn://svn.chromium.org/blink/trunk@177019 bbb929c8-8fbe-4397-9dbb-9b2b20218538