Try to fix crash because of InlineBox deletion in a cached subsequence

Don't know why the crashes occurred on bots. Couldn't reproduce the
crashes reported by clusterfuzz locally. Based on the stack, the crash
are because of deletion of an InlineBox in a cached subsequence.

This partly reverts https://codereview.chromium.org/2160983007/.

BUG=619630,628117
R=chrishtr@chromium.org

Review URL: https://codereview.chromium.org/2170583003 .

Cr-Commit-Position: refs/heads/master@{#406925}
3 files changed