Replace ASSERT_NOT_REACHED with NOTREACHED

ASSERT_NOT_REACHED is deprecated and its usage causes warnings in the
check-webkit-style presubmit. This patch replaces ASSERT_NOT_REACHED calls with
the recommended replacement, NOTREACHED.

Review-Url: https://codereview.chromium.org/2109333002
Cr-Commit-Position: refs/heads/master@{#403102}
35 files changed