This fixes a corner case where optimized code could still be reachable
through the optimized code map, even though unoptimized code for any
inlined function might have long been flushed.

R=ulan@chromium.org
TEST=cctest/test-heap/Regress513496
BUG=chromium:513496
LOG=n

Review URL: https://codereview.chromium.org/1415683011

Cr-Commit-Position: refs/heads/master@{#31857}